In the Steam store and launcher, your game is flagged as “not compatible with macOS 10.15 Catalina”. However, I’ve tested it and it runs perfectly fine. The issue is that there’s a box you need to check on Steamworks to tell Steam that you provide 64-bit binaries for MacOS. Under Steamworks > App Admin > Edit Steamworks Settings > look for "Supported Operating Systems”, check the box for "64 Bit Binaries Included”. That should make it show up properly on Steam for all your Mac players!
