I couldn't enter GTA V/Online, have access to Rockstar Games Launcher at all due to some newer update or when changing back to my main crew, or even after changing graphics settings too many times. Many players have similar problems.   Go to Documents\Rockstar Games\GTA V and delete Settings.xml to have default settings. That might be the problem. If you don't wanna lose that file for whatever reason, just cut and paste the settings.xml to a different folder and start the game.