I'm running Polyphone 2.3.1 on a 2022 MacBook with Monterey 12.4, but had this problem before on an older Mac as well. I have yet to successfully export anything from any version.
I simply cannot save any changes. If I make a new soundfont, the sample will appear to load and play fine, but when I import it to MuseScore to use it, no sound plays. It doesn't matter whether I use the save button, the "save as" dialog, or the "export" dialog. If I start with a working soundfont and edit it, the changes will not be reflected in the output, even if I save it to a separate file from the original. Any ideas what I might be doing wrong?