I'm having the same problem, I don't remember the password but when I try to reset it using the email it says that It's not valid. It's possible that they wiped everything.
I don't think they wiped everything. If that's the case they should have announced it and I shouldn't be able to log in as well, but I tried and it went through. Maybe it has something to do with this:
2018-04-21 08:25 - Nova Exchange, now exclusive for previous users
Only the users that was able to register before we stopped registration in the end of 2017 and who has also accepted the new ToS of the new owners are now able to login. New owners will decide when to enable deposits, new user registration and start listing new coins. We hope you will enjoy the service from the new management and support team! Thank you for staying with Nova Exchange! /Good bye from old management and support team
I don't remember if there was some kind of confirmation for the new ToS though, and that I accepted it to be able to log in until now. Why not contact them first?