What Download link are you trying? Mega.nz Folder or Other Mirrors? And What Browser are you using? I use Chrome and it downloaded fine using Mega Sync.
I tried downloading it through the Itch.io app and Mega.nz, but the app just goes right to the incompatible third-party website message, and the Mega.nz download just shows as a blank file.
That is odd, If you use a VPN, You might disable that while it downloads, Your anti-virus might also be affecting the download, Other than that, I do not know. Hope you get it fixed!