Tried both ways and the same problem occurred. Any particular way I should contact staff about this issue?

So my last thread got locked for some reason, but the server doesn't seem to accept my username and password?
I know for a fact that I have typed them correctly, as I have already logged in to this forum multiple times. Every time I log in to the client or the browser version, however, it shows me the screen asking me to register. What? :-\

So I created an account yesterday and when I logged in, it told me to register, which I had already done. Anyone have any idea what's going on? Thanks in advance.