I assume you've tried their chat support function?  I don't know why you're having problems with Kucoin, but they're not exactly known as an exchange that has lousy customer service (like Coinbase or *gasp* Yobit).

What exactly is your account locked for?  Did you forget your password after not logging in after a while or something?  One more question: You say you're accruing interest.  Do you have your ETH there on Kucoin's lending platform?  I'm just curious about that; it doesn't make a difference as far as your account being frozen.

I suspect you'll be able to recover your funds, because Kucoin is pretty decent.  If you do, could you please update this thread (or if there are any updates as far as their communications with you)?