This error message or notification supposed appear on a new registering account and not for old user like you then the website of the casino has an issue to solve. All the methods to see if the problem was from your end was abortive. If you can have access to the support team contact them and tell the the situation at hand and also take the email from the site and message them.

I think 0xbet is a new casino but the complains are too many, they have to do well in the forum to create that trust from users.