Yo, I faced this problem for a month and its just annoying, I finally found fix.
Go to :Call of Duty Modern Warfare 3\IW4M Admin\Log
Check for GSC integration enabled = null for x.x.x.x:27017
The same x.x.x.x:27017 is your server Ip
Type in console "/connect x.x.x.x:27017"
And you are done.