I can no longer create or edit Apple Music Playlists

Since last week, I edit a playlist name - click 'done' - nothing saves, it's like I haven't just typed any changes. Occasionally the name will change in the main window but never in the sidebar. When I close and re-open Music, zero changes have been saved to playlist names in main window or sidebar even if it changed in the main window before I saved.

Same thing if I try to create a new playlist - I select file - new playlist - type in a title - click done and...nothing appears. Used this buggy, counter-intuitive replacement for iTunes since Apple introduced it and never had this issue. I use it to organise my own mp3s that I upload. What gives?

The only thing I can think of that is different is that I activated a new iPhone a fortnight ago and recently downloaded an update to Music so that the iPhone was compatible. Currently running Sonoma 14.6.1 on a 16"/ 2019 Intel Macbook Pro