I started a thread elsewhere thinking the problem was with downloaded music but it seems to be wider.
When i switch duo Catalina i synced all my music to iPhone. I have 2000 albums and don't want to do that everyone so I manually manage music. That seemed to work fine for a couple of days. But today i had 2 new album s- 1 downloaded from Amazon Music and 1 a new CD. Got both on my mac ok but could not manually transfer to iPhone (manually manage checked) – dragging did not allow me "into" the iPhone. By accident ai dragged across and created a playlist which I could transfer to the phone (and then delete the playlist so leaving just the album). I'm sure that's not the intended way – nor is it how I was doing it the other day. Any suggestions? I'm not sure where the problem lies – device, system so not sure which one to tick below