I appreciate what you are saying however i can confirm the following
1. I have removed all files relating to GSX before reinstalling
2. I have reinstalled using the latest stand alone add on Manager
If you really did what you said here, it's quite normal GSX won't work. According to your report, you Uninstalled GSX, and reinstalled JUST the Addon Manager. How do you expect GSX to work, if you uninstalled GSX and haven't reinstalled it ?
3. I can confirm that this has been installed based on the fact its in add on Manager
Having GSX in the Addon Manager doesn't mean it's installed, it only means you can check its activation status, purchase it, reactivate it, etc.
But to USE GSX you must INSTALL GSX, using the GSX installer. Installing just the Stand-Alone Addon Manager, after a GSX removal, won't work. And of course, since the GSX installer contains everything needed to work, if you install using the GSX installer, there will be NO NEED to reinstall the Addon Mananger too.