Both have PP version 14.5.0 (Build 51) and both running Windows 10 Pro.
One machine is running Win10 Pro version 2004, the other 1909, but problem manitested itself before update to version 2004 in October. I first noticed the problem in June, so I doubt the difference in versions (1909 vs 2004) is a clue to solving the problem.
Could there be some codec installed that I need to remove in order for the file to be read correctly in PP?
I doubt the OS version is the culprit and Cineform should be decoded natively in PP so you shouldn't need any codec installs. Was the file brought in via the Media Browser or straight into the Project panel? It might be worth clearing the media cache on one or both machines and bringing it in fresh to see if it changes on either machine.
Without exception I always bring media into projects right clicking in the Project window, and selecting "Import...". Never use the Media Browser.
I have cleared the media cache on both machine and one small interesting thing happened. On the problematic machine PP actually tried to create a peak file. I had a moment of optimism, but still the same result: The audio is silent.
I also tried renaming %AppData&\Roaming\Adobe\Common to something else, thus PP recreating it. Didn't help either.