I may have posted this elsewhere .....
Aspyr have sent out notice that Mac OsX Catalina will not support 32 bit applications. This includes CoD4. They may or may not upgrade to make it 64 bit but they weren't too clear.
Aspyr's notice: https://support.aspyr.com/hc/en-us/articles/360000214186-MacOS-Catalina-64-bit-32-bit-and-related-Questions
Having said that: https://www.aspyr.com/games/call-of-duty-4-modern-warfare
One solution is to create a partition on your drive, install OSX Mojave and reinstall CoD 4
Here's how to partition the drive: https://support.apple.com/en-ca/guide/disk-utility/dskutl14027/mac
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