Are you running Band-in-a-Box only from your Mac internal hard drive? Are there any case sensitive file systems involved? Select the hard disk in Finder and press Command+I (Get Info).
We've created a special debug app that might help us solve this problem.
1. Download/unzip:
https://nn.pgmusic.com/pgfiles/support/misc/temp/Band-in-a-Box_2023-font-debug.app.zip2. Copy the .app to your Band-in-a-Box folder and run it. NOTE: this test app is not notarized, so you need to right-click and select Open in order to run it.
3. Open the Notation Window, and then check your Band-in-a-Box folder - there should be a FontErrorDebug.txt file created. Please send this file or paste in the contents.