Garrysmod:I was banned from my web console

From Serenity Servers Support

The webconsole uses the Rcon protocol for source games.
If you enter in the wrong password too many times, you will get banned.

However the solution for this is quite simple, simply restart your gameserver.

To avoid this in the future, please follow this and change your rcon password. Game Servers:How to change my servers RCON password