Dude there are some required deposits when your digital assets exceeds a great amount (e.g. 2 BTC) and that is for the safety of the account.
requiring to deposit more coins to withdraw current balance is pretty absurd, and smells like scam
any service requires a deposit to unlock/enable withdrawal of your own coin is definitely a scam
whatever digital asset in that account most likely is fake and put in place as bait to lure greed people
if that asset/coin is truely yours from the beginning, the service probably only require KYC stuff