Hey @teowey! Thanks for letting us know! To help us debug this, could you send us the contents of the game's log file? It should be located in the "Library/Application Support/Oh My Git/logs" in your home directory. The newest file in there would be interesting to us, can you find that? You can go to the Library directory by pressing Command+Shift+L in the Finder.
Viewing post in Doesn't work on my macOS Catalina 10.15.7
Feel free to send an email to the address at the bottom of this page, for example! https://ohmygit.org/press/