media_player_mpy - Exp on Mac not showing same overview as on Windows

Hello! I'm helping an RA get ready to run an OpenSesame study that includes some video stimuli. The study runs fine on Windows machines, but opening the exact same .osexp file on a Mac (from the same shared drive), we get errors saying that specific video files are missing. However, searching the file pool reveals the exact same set of mp4s on both computers; what does look different between the two is the overview pane, which on the Mac is missing all the media player items that refer to mp4s. Running the experiment works on PC, and fails on a Mac.

What we've done so far on the Mac (a Macbook Retina 13" from late 2020 running Monterey OSX 12.4)...

• Install XCode Command Line Tools, homebrew, and Python3 (initially 3.10.6, then later 3.7.10)
• Download OpenSesame for Mac using `brew install OpenSesame`
• Download as many relevant required packages as needed (including numpy, pyyaml, ffmpeg, mediadecoder, moviepy, portaudio, pygame, and pyOpenGL) using brew or pip. (The pip we were using was `python3 -m pip install PACKAGE` rather than `pip install PACKAGE`)
• Download media_player_mpy (from https://github.com/open-cogsci/opensesame-plugin-media_player_mpy/), expand and move it to the plugins folder under Applications/OpenSesame.app/Contents/Resources/plugins, run `python3 setup.py install` and `python3 setup.py build`
• (setup.py had one command that couldn't be parsed as-was, so I changed line 27 to d=yaml.full_load(fd) )
• Confirm that all the settings and preferences matched between the Mac and PC.

I think something's gone wrong with the media_player_mpy plugin, but I can't figure out what! Any suggestions for troubleshooting? Thanks so much,

-E