Sometimes people leave mod files in an extra folder as a result of extracting the folder from the zip archive, so I try to check that. The ability to manually assign those images to slaves rules out a lot of problems.
There appears to be nothing wrong with the tags. If a game is started with an adult human female slave, they should receive that or another similarly tagged image. You didn't post the file extension, though I doubt that is the problem. Anyways, the Godot Engine will only load images with the following extensions: png, jpg, webp.
I just realized the problem. The Bugfix V6 organizes the way races are handled. portrait.gd in this mod uses "globals.allracesarray" which was retired. It just needs to be replaced with "globals.racefile.groups.all".