Can't sync MacBook Air M1 music to iPhone 12 Pro Max

I signed out as a user (not from iCloud, I left that alone) and the logged back in. At first, I was rebooting but it turned out to be unnecessary in my case.

I chatted with Apple support, they think something went wrong during the latest update install. Their solution is to run a reinstall over the OS. I might do that at a later time, but signing in and out is an enough of a workaround short term.

I don’t think you need to subscribe to Apple Music since it doesn’t anything to do with this particular issue.

Hello,

I have a similar issue after the most recent update. The only workaround I have found is to fully sign out and back in. Then it works once. After that, it either fails to sync how you described, or it thinks some songs can't be played on the phone and it removes them. Until you sign out and back in again.

UPDATE:

I updated to 14.6 and the issue persists. I guess the plan is to re-install the whole OS at this point. However, I might wait until OS 15 comes out this Fall. The workaround still works though, so that's good.