Hi, Void War currently does not support macOS however in the future we will definitely release a Mac version. This will happen some time after the Steam release. If you have already bought the game here, we will be able to transfer your game to Steam when it eventually launches there.
If you want to get a refund the proper procedure is to contact Itch support about it: https://itch.io/support
Lastly, we have heard from some of our players that the Windows version of the game (the one you have) works with CrossOver, a Windows emulation software for Mac. We cannot guarantee it will work, but if you really want to play it right now on Mac, CrossOver might be worth a try.