iOS MuseScore app doesn't play an mscz filr

I created an mscz file (for two recorder parts) in MuseScore 4.

When I tried to load the file and play it on my iPad, using the MuseScore app, it does seem to be uploading to my device but I get a blank screen instead of the score, and it won't play. Another "clue" is that the file isn't the file name. It just gives me a number: 1426181924.

Other mscz files have the file name--like "Canarios." They can be played.

Any idea what's going wrong?