In order to allow gametracker to function properly on your teamspeak server you need to allow the guest group to retrieve server infos.
- open your teamspeak3 client
- connect to your teamspeak3 server as administrator
- press CTRL + P
- enable the "advanced permissions system" and confirm with ok
- press CTRL + F4
- click on "guest"
- select "show names" on the botton of the window
- set the permissions as showed in this image (double click on the lines in order to enable them):