P.s on the new account I didn't use any bonus other than the free spin claim after email/phone verification
This could be a problem if your old account has claimed the free spins ,can you make sure your old account doesn't claim free spins?
For cashback I don't think it's part of the promotion I see this program in almost all casinos. however I wish you all the best.
I think it also depends on the type of promotions they were running at that time and now? Because even if free spins were claimed, games may be different and if Op didn't misuse FJ's promotions by "withdrawing from old account through the use and growth of free spins' funds", then they are eligible to use the site normally.