You could try to Download it from the Itch.io Site (https://verrial.itch.io/projectaether) there is an Download Button, then u get an .zip file u Extract the file to an Folder and then run the ProjectAether.Exe
No, you could Download the Itch.io App (https://itch.io/app) and try to Download and run it over this way, but Tell me real Quick, what is the Problem with the Game, dont starting, crashes?