Cannot sync new music after AM cancellation

I redeem the free trial to check out the music quality but decided didn’t like it and cancel it… after that I cannot sync new music to my phone and keep seeing “iPhone cannot be synced because sync session failed to finish” prompt

I only edited my name on the music app during the trial and did not sync my library when prompted cos I was worried my files might be affected. my files are locally stored but I read that the existing files in app might be screwed up after cancellation so I did not want to sync my library.

anyway I did a lot of trial and error…finally it synced successfully after de-and-reauthorize on iMac but now it doesn’t work again! and I don’t see any sync library option on my iMac and iPhone either…. help please!