If you are unable to join your new CS:GO server, this is because recently Valve require all server owners to generate a token. This token links the game server to your Steam account.
You can create a token for your game servers by going to Valve’s official steam gameserver login token page here:
http://steamcommunity.com/dev/managegameservers
APP ID: 730
Memo: Anything. e.g. LOW.MS Server
1. Copy the generated login token.
2. Login into the control panel at https://control.low.ms
3. Click Configuration Files
4. Click Text Editor for Server config file (csgo\cfg\server.cfg)
5. Add the following line anywhere in the file:
sv_setsteamaccount login_token
Where login_token is the login token you copied earlier.
6. Restart your server.
Order your CS:GO server now here