If they don't reply to your tickets, it either means that they don't know how to deal with the situation (due to the pressure coming from the US government), or they simply don't have the time (which in this case would be somewhat amateurish). If your account was enhance verified, you would have the option to join their slack through an invite. In case you made use of that, and have access to their slack, contact them there. If not, then try to look if their IRC channel #bittrex is still alive -- I remember this was quite a fast way to contact the operators.