Hi! Sorry about this issue. There are some compatibility issues with Catalina. There are some workarounds, which you can read here:
/t/517191/macos-catalina-compatibility
The easiest workaround (imo) is to redeem the included Steam key and launch it from there. Let me know if you still are having issues!
Unfortunately, I can't fully support Catalina at this time. There is a workaround to get it to work, but it requires a bit of technical know-how.
To quote another thread:
1. Double-clicking the app gives the error, "The application "AShortHike.app" can't be opened." Open a terminal window, go to the folder containing AShortHike.app, type "cd AShortHike.app/Contents/MacOS", then "chmod +x AShortHike".
2. Double-clicking the app gives an error that the app can't be opened because MacOS can't verify the developer. Instead, two-finger click on the app, then select Open from the context menu, then Open from the warning dialog.
Apple has made it difficult for developers without Macs themselves to authenticate their apps for their platform.
