Large Apple Music playlists not syncing to iPhone and iPad
I subscribe to Apple Music. I have 3 large holiday playlists (508, 600 and 379 songs respectively) that date back to the days of CD's and iTunes. They appear on my iMac (Retina 4K, 21.5-inch, 2017) , but don't synch to my iPhone (iPhone 12) or iPad (iPad 10th gen). I've tried renaming them coping the songs to new playlists with different names, made sure I was signed in on my account on all devices, rebooted multiple times, unsynced and resynched and deleted and reinstalled Apple Music on the iPhone and iPad.
It appears that every other playlist I own (284 in total) synch just fine.
I'm out of ideas on how to get these three playlists to synch. Can