Add To Device not working (Macbook to iPhone)

For reasons too long to go into, I recently erased my music library from my iPhone (15 Pro Max - 18.1.1).

I am currently trying to add music back from the Music App on my MacBook. I have been adding tracks by left clicking on batches and selecting "Add to Device". I managed to get about 3/4 of my library copied before xmas. I now can't get the rest of it to move (yes, there is plenty space available).

I seepect tracks, right click, Add To Device, Chose my iphone.....nothing.

I've backed the phone up, just to be prompted to enter the password to give access. No change

Any suggestions of what I need do?

The phone is connected to the laptop physically - this is not over wifi

Macbook Air - Sequoia 15.1.1