I am playing the game through steam and all I get when I /ban someone is "This player does not exist."

I'm also on steam. When I /ban somebody I get "Your demand has been taken into consideration." as usual.

are you copy pasting the name of the person you want to ban or manually typing it? there's a high chance of typos if you type it in yourself, a lot of mice deliberately spell their names in ways that are hard to copy, or use characters that look like other ones in the context of the name

You're no longer able to ban the room creator, and this is what the output is when you try.

A couple of people on IRC have been getting the same issue for the past couple of days. One user tried votebanning himself after trying to voteban the other user, and they got the same message. The second guy tried vote banning a hacker and most likely the hacker was not the first mouse in the room. The issue has been forwarded to the admins from what I've been told.

Well, it seems to work now, maybe it's some random occurrence?

I got that too when I was playing on a browser

This should be fixed on the next restart.