If you enter your rcon password wrong too many times on the interface to create a lobby, you will end up with an error saying something along the lines of "Connection Refused" eventually. This is because after a certain number of failed rcon attempts your server bans whatever ip was attempting to use rcon for using a bad password too many times. There is an easy way to fix this:
1. Open up TF2, and make sure you have the console open.
2. Type rcon_address [your server ip]:[port] and hit enter
3. Type in rcon_password [your correct rcon password] and hit enter
4. Type in rcon removeip 188.8.131.52 and hit enter*
And there you go, you can create tf2center lobbies on your server again!
Edit: There are now more ips than this. I'll try to get a list of them.
* This should be the current IP of tf2center.com; try to resolve this using "ping tf2center.com" in your cmd/terminal.
Edited by ninjaMooCow, 01 May 2016 - 07:02 PM.
Updated domain name / IP