Sorry to hear! It may be because Gatekeeper is determining it as unsafe. Can you try running it through the itch app if you aren't already?
Otherwise, you can try following the instructions under "If you want to open an app that hasn’t been notarized" on this link:
https://support.apple.com/en-us/HT202491
Let me know if one of those works, either way we'll figure it out!