This happened before iOS 14, but much less frequently. Since the release of iOS 14, many users have reported to me that songs they add to a playlist through my app take a long time to appear (and sometimes never appear). The web service responds 204 No Content as expected, so I'm suspecting that there may be a bug in the backend that handles this service, or in the Music client apps that are not syncing the latest changes to playlists.
I managed to reproduce this here too. All I had to to was to call this endpoint a few times with different tracks and open the Music app to check it out. The tracks sometimes appear as expected. But sometimes they appear on my Mac and don't appear on my iPhone. Sometimes they appear on the iPhone, but not on the iPad. And I even saw one time they appearing on the client apps, but not in the web interface (music.apple.com).
My question is: do I need to do something different on my end after calling this endpoint, or this is a problem with the backend service and/or client applications?
I managed to reproduce this here too. All I had to to was to call this endpoint a few times with different tracks and open the Music app to check it out. The tracks sometimes appear as expected. But sometimes they appear on my Mac and don't appear on my iPhone. Sometimes they appear on the iPhone, but not on the iPad. And I even saw one time they appearing on the client apps, but not in the web interface (music.apple.com).
My question is: do I need to do something different on my end after calling this endpoint, or this is a problem with the backend service and/or client applications?