Soundfont not uploading with score

I tried to upload my score multiple times, with 2 soundfonts installed (Aegean Symphonic Orchestra and HQ Orchestral Soundfont Collection) on top of the default, which was not used in my score anyways. I'm on Musescore 2.3.1 on a windows 10 computer, and followed all instructions for uploading the score with soundfonts (i.e. upload in Musescore program directly with soundfonts saved to score, mixer settings seem fine, checked upload score audio), yet the soundfonts don't upload with the score.

The progress bar initially is fine for exporting the score (its not particularly long, only 7 pages), which takes just a few seconds and has visible progress, but when it starts uploading, the progress bar starts at 0%, then goes to 2%, then back to 0%. This takes well over a minute or longer, and no progress seems to be made. After a while, it just stops and everything goes back to normal usage. There's no message saying if the upload was successful or not, but I checked the score online, and the score was published successfully. However, when performing playback, the audio is using default audio, and there is no additional audio source attached. Is there something I'm not doing correctly, or is there an actual issue with uploading scores with soundfonts?