Your problem is NOT the loss of activation.
Since you said you are also missing the GSX menu, the most likely cause for this is that the Couatl module hasn't started, most likely because your antivirus might have blocked it, mistakenly assuming it might be a threat (it obviously isn't, its just your antivirus catching a false positive)
Try to reinstall GSX with the antivirus disabled, and before starting the sim, add the whole Addon Manager folder to the antivirus exclusion list.