PSO2 Tweaker don't start game. When I click "Start PSO2" the Microsoft store opens on the Gaming Services page and that's it, nothing further.

that happened to me before, the store doesn't detect the .exe of the game unfortunately there isn't much you can do and the only way to 100% fix that is reinstalling the game

Uninstall the game, restart computer, install pso2, launch game but don't start playing close it then open tweaker and launch game from there. You should not get or see any problem after this until they update/hot fix something if so then repeat this madness again.