First of all, the title is quite misleading and almost “wrong-ish”.

The jiva is an eternal energy of Krishna and within this energy, another energy can´t be inherent.

“Tatastha does not change into svarupa-sakti. But even before getting the siddha-deha, the tatastha becomes imbued by svarupa-sakti. That is called getting sthayi-bhava. The siddha deha is not a physical body as we have experience of. It is a bhava body.
I am sure you have come across a statement somewhere that says that Srimati Radhika is Mahabhava-svarupa. So the tatastha who is imbued with svarupa-sakti, like an iron rod made red hot by putting it in fire, is now linked to a body consisting of svarupa-sakti. There is oneness because the sthayi-bhava does not make the tatastha feel that he is having something exterior in him.”
(Srila Satyanarayana das Babaji)

Why is the eternal svarupa of the jiva not inherent in the jiva?

1)

The jiva is an eternal energy of the Lord, called “tatastha-sakti”.
It is the energy inbetween the Lord´s external energy (maya-sakti) and His internal energy (svarupa-sakti).

Eternal means eternal.

krishnera ‘nitya-dasa’ krishnera ‘tatastha sakti’ ‘bhedabheda-prakasa’
(Caitanya Caritamrita  Madhya-lila,  20.108)

“The jiva is the marginal potency of Krishna and a manifestation simultaneously one with and different from the Lord.”

2)

The eternal svarupa of the jiva, the siddha deha, is of the svarupa-sakti, the internal energy of the Lord.

vaikunthasya bhagavato jyotir-amsa-bhuta
vaikuntha-loka-sobha-rupa ya ananta murtayas
tatra vartante tasam ekaya saha muktasyaikasya murtir bhagavata kriyata iti
vaikuntasya murtir iva murtir yesham ity uktam
(Priti Sandarbha 10)

“In the spiritual world, the Supreme Lord has unlimited spiritual forms. They all are expansions of Himself illuminating that world. With each one of those forms, the Lord enjoys pastimes with a single individual liberated soul.”

vasanti yatra puruṣāḥ
sarve vaikuṇṭha-mūrtayaḥ
ye ’nimitta-nimittena
dharmeṇārādhayan harim
(SB 3.15.14)

“In that place all men reside with forms like the Lord and they worship the Lord with unmotivated service. They have forms like the Lord.  They have no personal motives (animitta) impelling them (nimittena) to worship.  Ārādhayan means that they worshipped since ancient times.”

tvaṁ bhakti-yoga-paribhāvita-hṛt-saroja
āsse śrutekṣita-patho nanu nātha puṁsām
yad-yad-dhiyā ta urugāya vibhāvayanti
tat-tad-vapuḥ praṇayase sad-anugrahāya
(SB 3.9.11)

“O Lord! You, Who are approached by being heard about, seen and directly served,
enter and remain in the lotus of your devotee’s hearts infused with bhakti-yoga.
Much praised Lord! By your mercy, you bestow to them spiritual bodies appropriate to the mood they cultivate during sādhana.”

3)        

Bhakti is not “inherent” in the jiva-sakti.
Bhakti comes from bhakti.
Bhakti is given by someone who has bhakti.

brahmāṇḍa bhramite kona bhāgyavān jīva;
guru-kṛṣṇa-prasāde pāya bhakti-lata-bīja
māli hoiyā kare sei bīja āropaṇa;
śravaṇa-kīrtana-jale koroye secana

 “When a living entity while wandering throughout the universe in different species, attains good fortune by the causeless mercy of guru and Kṛṣṇa, then only he can get the seed of the wish-fulfilling bhakti creeper. He becomes a gardener who received the seed and waters it by hearing and chanting of Kṛṣṇa.”
(Caitanya-caritāmṛta, Madhya 19.151-51)

4)

Bhava and finally prema manifest themselves in the heart of the jiva, which was being “cleaned” by sadhana-bhakti. It is not “already” there, waiting to be “awakened”.

kṛti-sādhyā bhavet sādhya-bhāvā sā sādhanābhidhā |
nitya-siddhasya bhāvasya prākaṭyaṁ hṛdi sādhyatā || 
BRS 1.2.2

“Devotion which is enacted through the senses and which leads
to the self-manifestation of bhāva-bhakti, is called sādhana-bhakti.
The self-manifestation within the heart [of the practitioner] of the eternally existing transcendental affect of devotion (bhāva) is known as the completion stage of devotion.”
(Bhakti Rasamrita Sindhu 1.2.2)

Srila Jiva Gosvami’s Durgama sangamani commentary:

bhāvasya sādhyatve kṛtrimatvāt parama-puruṣārthatvābhāvaḥ syād ity āśaṅkyā—nityeti |
bhagavac-chakti-viśeṣa-vṛtti-viśeṣatvenāgre sādhayiṣyamāṇatvād iti bhāvaḥ

“A doubt may arise that since this state is achieved [sadhya], implying that it is artificially produced, it is not the ultimate goal. The second line responds to this doubt by saying that is is eternal, and simply appears within the heart. That is because its appearance [and not its creation] will be accomplished in the future by the special actions of the most excellent transformations [samvit and hladini aspects] of Bhagavan’s svarupa sakti [which are perfect and eternal].

5)        

The metaphor of the “bhakti-lata-bija” is a wonderful metaphor by Sriman Mahaprabhu to demonstrate how our bhakti grows from an initial “seed” to a full-blown flower.

Nevertheless, it still is a metaphor, albeit a very genuine one. Sri Gurudeva does not give the disciple a transcendental seed to “swallow”. This brilliant metaphor stands for a transmission of spiritual energy from the heart of the one who has it to the one who desires it.

“Watering that seed with śravaṇa and kīrtana makes the bhakti creeper sprout in the field of the devotee’s senses. Favourable service to the Lord is the root of that creeper. The very life-force of bhakti is to give pleasure to Śrī Kṛṣṇa.”
(Srila Ananta das Babaji Maharaj)

6)        

The “bhakti-lata-bija” does not contain the siddha deha in its “seed-form”.
The siddha deha is eternal and is not “packed” as a seed in the bhakti-lata-bija.
The jiva is not pregnant with the seed of the siddha deha.

7)        

Prema is not already “there” in the jiva, sleeping, only waiting to be awakened.

nitya-siddha kṛṣṇa-prema ‘sādhya’ kabhu naya
śravaṇādi-śuddha-citte karaye udaya
(Caitanya Caritamrta Madhya 22.107)

“Krsna prema is eternally perfect (nitya-siddha kṛṣṇa-prema) and it cannot be generated by anything (sādhya’ kabhu naya). It arises within the heart that has become purified by practices such as hearing, etc (śravaṇādi-śuddha-citte karaye udaya)”.

Prema descends into the suitable heart of the jiva. The jiva has the potentiality to RECEIVE this most wonderful PREMA as the culmination of bhakti.

Mukunda dasa Gosvami says: nitya-siddha-bhakteṣu śuddha-sattva-viśeṣa-rupatayā sadā vartamānasyātra svayaṁ sphuraṇān na kṛtrimatva-śaṅkā) – “The pure sattva which is ever present in the nitya siddha devotees manifests itself [in the heart of the practitioner devotee] and thus should not be seen as artificial.”

8)

The jiva is not “sat-cit-ananda” like Sri Krishna.

In case of the jiva:

sat => eternal

cit => cognitively aware (of his own field [body])

ananda => free from suffering

In Paramatma Sandarbha (28), Sri Jiva Gosvami explicitly says that the self is devoid of knowledge, although conscious by nature, and it lacks bliss although free of any material misery. In other words, it has the potential (svarupa yogyata) to get knowledge and bliss but not yet the functionality (phalopadhayi yogyata).
(check Paramatma Sandarbha and Tattva Sandarbha for more references)

The jiva is like a drop of the ocean. Krishna is the ocean. The drop can have no waves. You can´t surf on a drop. Krishna´s form of sat-cit-ananda is different.

9)

“Jivera svarupa haya” doesn´t mean that the svarupa is inherent in the jiva.

jivera ‘svarupa’ haya –
krishnera ‘nitya-dasa’ krishnera ‘tatastha sakti’ ‘bhedabheda-prakasa’
(Caitanya Caritamrita, Madhya-lila,  20.108)

“The jiva’s essential nature is to be an eternal servant of Sri Krishna. The jiva is the marginal potency of Krishna and a manifestation simultaneously one with and different from the Lord.”       

“Svarupa” here means ‘essential nature’. It is our essential nature to be a servant of the Lord. Nature is not the same as eternal spiritual form. Nature here is ONE, our forms can be MANY.

From Anuccheda 19 until the end of Anuccheda 47 of his Paramatma Sandarbha, Srila Jiva Gosvamipada describes the svarupa of the jiva, provides sastra pramana for the qualities of the jiva’s svarupa and refutes Advaita (mayavada) concepts of the jiva. There is not one instance in this whole discussion on the svarupa of the jiva where he admits any type of svarupa-bheda (differences in the svarupa of jivas).

10)      

Krishna has not “put” a taste/attraction already in a “pre-fixed” way into the heart of the jivas.

The seed of RATI is sown by sadhu-sanga. THIS IS WHAT Brihad Bhagavatamritam 2.4.190 is all about:

vicitra-līlā-vibhavasya tasya samudra-koṭī-gahanāśayasya vicitra-tat-tad-ruci-dāna-līlā- vibhutim uttarkayituṃ prabhuḥ kaḥ

anvaya and word for word meaning:

kaḥ =who?, prabhuḥ= is capable, uttarkayituṃ= to conjecture, tasya= His, tat-tad-ruci-dāna-līlā- vibhutim= the opulence of pastime of giving various tastes, vicitra-līlā-vibhavasya= one who has the majesty of performing varied lilas, samudra-koṭī-gahanāśayasya= whose heart is deep like millions of oceans

Translation: “Who is capable of conjecturing His opulence of the pastime of giving various tastes? He has the majesty of performing varied lilas and His heart is deep like millions of oceans”.

Tika:

“A doubt is raised: Hṛṣikeśa is the prompter of the potencies of cognition and action of every one. Then why does He not give the best process of worship equally to everyone? In response to this doubt Nārada Speaks the present verse (2.4.190). [The commentator explains the compound word vicitra-tattad-ruci-dāna-līlā-vibhutim.] [He] distributes (dānam) to them [the various people who take to different types of worship] the various types of (vicitrāṇām) specific bhāvas (rucinām) or relish. If the reading is tāna, instead of dāna in the compound word, then the meaning is that He expands [instead of He distributes]. This indeed is His Play (līlā). Who (kaḥ) is capable(prabhuḥ) of conjecturing or ascertaining properly (uttarkayitum) the grandeur (vibhutim) of His līlā. Indeed, there is no one. The reason behind this incapability is given in the adjective samudra-koṭī-gahanāśayasya – one Whose intention (āśaya) is deeper or more mysterious (gahana) than millions (koṭi) of oceans (samudra). The reason behind expanding [or distributing] various types of relish is given in the adjective vicitra-līlā-vibhavasya – one Who has various types of majesties (vibhava) of His myriad (vicitra) līlās. Otherwise He will not accomplish the sweetness of the majesty of His various līlās – This is the sense.”
(Satyanarayana das Babaji)

Now, how does Sri Krishna distributes/gives/bestows (DANA) the various tastes to the various people who take to different types of worship?

He does this via the gateway of the mercy of His devotees.

Srila Jiva Goswami:

“Devotee association acts as the seed of rati. Through association with various types of devotees, various types of sadhana which are like watering the seed will be performed.”

Nowhere does Srila Jiva OR Srila Rupa Goswami write that sadhu sanga brings out the inherent rati of the jiva. Nowhere.

11)      

Every individual soul is qualified to become Rādhikā’s maidservant; this is the great, rare gift of Śrīman Mahāprabhu.

According to the “everything-is-inherent-and-prefixed” vada, only a few are then able to receive this highest gift of unnatojjva rasam sva bhakti sriyam, namely those who would have a “seed” of madhurya rasa already in their jiva-svarupa.

Now, where is the MERCY in that?????

Was Mahaprabhu an elitist?

No. He distributed this unnatojjvala rasa sva bhakti sriyam FREELY.

ataeva gopī-bhāva kari aṅgīkāra
rātri-dina cinte rādhā-kṛṣṇera vihāra

“Therefore one should accept the mood of the gopīs in their service. In such a transcendental mood, one should always think of the pastimes of Śrī Rādhā and Kṛṣṇa.”

So, by the mercy of Sriman Mahaprabhu, every jiva is eligible to receive this most wonderful gift, not only a few chosen, “prefixed” ones…every jiva has now the possibility by this mercy to become a maidservant of Srimati Radhika.

If we can accept this gift or not is a different matter.

12)      

If the svarupa of the jiva would be inherent, that would also mean that RAGA-BHAKTI would be inherent.

REFUTATION:

krsna-tad-bhakta-karunya-matra-labhaika-hetuka \
pusti-margataya kaiscid iyam raganugocyate
(BRS 1.2.309)

“The mercy of Krsna and His devotees is the only cause of attaining raganuga-bhakti. Some call this type of devotion pusti-marga.”

13)      

If the svarupa would be inherent, then GREED for raganuga-bhakti would be inherent.

Refutation:

“There are two causes for the appearance of the aforementioned sacred greed: The mercy of God or the mercy of another anurāgī devotee. There are again two kinds of mercy bestowed by a devotee: prāktana and ādhunika. prāktana means mercy bestowed by a rāgānugā bhakta in a previous life, and ādhunika is mercy bestowed in the present birth. The prāktana-devotee takes shelter of the lotus feet of a rāgānugā guru after the sacred greed has arisen in him, the ādhunika will get that sacred greed only after having surrendered to the feet of such a guru. It is said (in Bhakti Rasāmṛta Sindhu): “The only causes of the appearance of sacred greed is the mercy of Kṛṣṇa or His devotee. Therefore some call the path of rāgānugā bhakti also puṣṭi mārga (the path of grace).”
(Srila Vishvanatha Cakravartipada, RVC)

14)      

Holy association is the seed of love and affection for Krishna.

BRS 2.5.13:

“When a devotee’s rati, like a clear crystal, becomes similar in form to that of the devotee to whom he is attached, it is called svaccha-rati.”

Jiva Gosvami’s Commentary:

This verse shows how devotee association acts as the seed of rati.Through association with various types of devotees, various types of sadhana which are like watering the seed will be performed.

bhavāpavargo bhramato yadā bhavej
janasya tarhy acyuta sat-samāgamaḥ
sat-saṅgamo yarhi tadaiva sad-gatau
parāvareśe tvayi jāyate matiḥ
(SB 10.51.53)

“When the material life of a wandering soul has ceased, O Acyuta, he may attain the association of Your devotees. And when he associates with them, then devotion unto You will start, You Who are the goal of the devotees and the Lord of all causes and their effects”.

So, the seed of RATI is sown by sadhu-sanga.

vaiśiṣṭyaṁ pātra-vaiśiṣṭyād ratir eṣopagacchati |
yathārkaḥ pratibimbātmā sphaṭikādiṣu vastuṣu ||7||
BRS 2.5.7

“Specific rati appears per the specific impressions from previous experiences in the individual [jiva], just as the sun reflects itself on things like crystal.”