Not sure if this is related but i'm encoutering quite the same issue.
When i try to sign up, the interactive login window open, and then nothing.
opera_ByHq99bOgl.png
Any clic does nothing.. Can't login, can't delete account, waiting does not help.
I tried with Edge and i had the same issues, after few research i find something with Java, so I tried to uninstall Java and install x64 and x32 but still nothing for OperaGX whereas it helped for Edge.