ANOTHER Question about using soundfonts

So, earlier, I asked about making the "Upload score audio" checkbox clickable, and not grayed out (by making Musescore able to export to mp3). This worked, and I was able to check the box. Now, however, when I attempt to post the score to the website, it fails to do so with the "score audio".

When I attempt posting it, the "Uploading" progress bar starts at 0%, moves to a random percentage (say, 7%), drops back to 0%, and then tells me that "MuseScore couldn't upload the audio file".

Am I missing something? The score I tried this on was relatively large, so I tried again with a score with one note playing on one part, a violin, but I got the same result. I don't think it's my internet connection, as my upload speeds aren't that slow. Is it a problem with the site right now, or IS IT actually something on my end? Any help is appreciated. Thanks!