So it worked under 10.15 , is that right?
If so, this may need a fix from Apple - if they broke it they ought to fix it!
Might be worth doing a clean reinstall of the game though:
- move any valued save games elsewhere
- "uninstall" in Steam-Imperator
- manually delete both the Steam/SteamApps/common/Imperator AND Documents/Paradox/Imperator folders
- re-install game in Steam, run a Steam Verify when done.
- add imperator.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.
- start the game with no mods active and test
In particular you need to make sure there are no files or folders left under either the Steam Imperator or Documents Imperator locations, before installing again.
**File Locations on Mac OS X**
The executable and DLC folder are in Users/USER/Library/Application Support/Steam/SteamApps/common/Imperator/
On OS X 10.8.x and later, Apple have hidden the /Users/USER/Library/ folder. To see it go to the Finder, hit command-shift-G (ie Go To) and type in ~/Library/ .
The user files (settings.txt, error logs, saved games, gfx, mods) are in /Users/USER/Documents/Paradox Interactive/Imperator/ .