N3rdcub Ensure that native code debugging is enabled in Settings > Security.
If it is (that's the default) or you enable it again and the issue persists, you can try disabling secure app spawning in Settings > Security, rebooting, and seeing if the app works.
The app in question is using some crude anti-cheat or anti-tampering solution which seems to conflict with some of GrapheneOS' changes.
Likely related: https://github.com/GrapheneOS/os-issue-tracker/issues/1908