One of the following suggestions may help you:

    Your server is currently offline.
    GameTracker needs your server to be online before you can add it to our database. Please restart your server and make sure it's up before hitting ADD SERVER again.
    You entered the wrong query port.
    Please update your query port and hit scan again
    Your server is firewalled.
    Please turn off any firewall you have that may block scanning or whitelist the gametracker scanning IP addresses:
    208.167.241.190
    208.167.241.185
    208.167.241.186
    208.167.241.183
    208.167.241.189
    108.61.78.147
    108.61.78.148
    108.61.78.149
    108.61.78.150