The only other thing I can suggest to help investigate this would be for you to run the .exe from the command prompt (assuming you're on windows) and report back with what says for what's going on. At the same time I'd be happy for you to apply for a refund (only Itch.io themselves can initiate them unfortunately or I'd do it myself) and if that removes the game from your library, I'll provide another key while I investigate the issue and hopefully get it working for you.