I mean are you using Google chrome, Firefox, Opera?
I did not know that itch.io had an app to download games to your PC that was not from a browser! better try to download the version for Win here I leave the link https://mega.nz/#!ZU5TnITT!cKhB3X2QrlRpsr_KCkw_fk8BWTxCgeLIykMmhtpARGI