Aside from waiting for their response, you could try following up your ticket number in their twitter account and not here because from what I know the staffs are inactive here, it's no use.
Here is an example of a lucky guy who got a response from them (He had a similar problem): https://twitter.com/BittrexExchange/status/934499584260186112.
Try to be the first one to comment on their new tweets.
The Bittrex claim is BS, they are just trying to lock up funds.
That is if the user made his account a long time ago before polo changed their policies. If you will create a new account now, you will not be able to trade unless you verify your account.
But I seconded that bittrex seems so suspicious with their current actions. I understand that they also changed their policies but the way they handled it is so unprofessional