I just started gambling on stake and managed to pass my kyc level 2 verification some few days back, I don't even know if I've made it to platinum one, so I honestly don't know what it takes to be a platinum 4 ranked gambler on stake, but my guess is that, it must require gambling with lots of funds to achieve such rank, and also consider the fact that there is a limit to the amount of money a person can make through trading, and providing crypto services.
So depending on the amount of money involved, it can be understandable why they are not accepting trading, provision of crypto services as a genuine prove of funds.
@OP, If you have businesses or other investments outside crypto, then maybe you should try using that/those as a prove of fund.
You can find your VIP rank
here and see the benefits for all the available ranks
hereTo reach Platinum 4 VIP rank, you need to wager at least $2,500,000 (you can find more details about VIP Program
hereA full list of the acceptable documents for source of funds can be found
here. That list have been in the Help Center for quite a long time.
Also last, but not least, can the OP send me his Stake username (it can be in private, if you want to keep your privacity)? In order to find out what the real issue is, thats the first info we shall need