If Re logging into the site didn't work, maybe there is a sender issue. Create an alternate account and give those same perms to it, and then login. Other than that, i'm stuck as well.
There are a few things that could cause this. Your server could be having some trouble. Instead of typing the /unban and ect. Try to go to the banned players text file in your server file. Unban users from there. If this doesn't help post some more info! Hope this got to you on time.
