cant sync iphone with imac itunes song updates 20th Nov 2019

I updated both iphone and imac itunes today 20th Nov 2019. I used to be able to drag songs that I'd downloaded onto my imac into my iphone when plugged in to imac. Today I've tried to do this and no 'blue outline' shows up when hovering anywhere over my device file tree.

I then tried dragging the computer itunes playlist into the iphone playlist. This allows me to get a blue line, but when I check to see if its there, it isn't.

I then re-checked my sync options, making sure the playlists/artists that I wanted to sync were selected. they were. I clicked apply, itunes would run through its sync process, but the songs werent there.

Strangely, it worked the first time I did it today, and then when I realised some songs needed to be added to the imac itunes playlists, I did this, and then tried re-syncing to add the couple of extras in. This is where I'm stuck. They just WONT GO IN!!!

Have read all the info I can find on the internet, but nothing is working. I've even tried creating a 'test' playlist in imac itunes, and syncing this to iphone. it doesnt come up either. Is this a bug with the update??