What kind of device are you using? I'm not sure if this is relevant to you since I had a problem with Game Tuner a little over a year ago on my then-new Samsung S2 tablet. It wanted to update to a newer version and gave me a notification that my device was no longer supported. TSTO was impossible to play because the resolution was zoomed in so far. I had to go to APK Mirror and download/install a previous version of game tuner. The one I am using is 3.3.11. This has worked so far but there is one minor quirk. When I start my device, I have to immediately go into TSTO or it will be zoomed in. Strangely, it will stay at a decent resolution all day even if I close the game. It only reverts when I power off my device.
I hope this makes sense and can help you.