... I thought with OP being from non-sanctioned country and he supplied your team with supporting documents, it can be easily tackled...
since I was born in Russia (USSR) - it doesn't matter where (Bulgaria) and for how long (11 years without a break) I'm living - "you're under suspicion"!
That shouldn't be the problem, the suspension of activities on their platform due to the sanction are limited to the people residing in Russia and Belarus. Unless you can't provide a concrete evidence that you're accessing and currently residing in Bulgaria, the limitation shouldn't be applied to you.
What's the last thing they said to you regarding this matter?
Hi there.
Due to global sanctions on Russia and Belarus, CEX.IO, as a regulated entity, has implemented temporary measures. These include the suspension of deposits, withdrawals, and trading for accounts held by users residing in Russia and Belarus. [...]