How to reverse Itunes Match?

I use an iphone XS and itunes on PC.

A month ago I activated a trial subscription for Apple Music, used it for the month, then cancelled it.

All the music in my music library is music I own on CDs, that I have put into my iTunes myself.

After I cancelled the Apple Music subscription, I can't play about 80% of my own music library on my phone; when I try, I get the message "iTunes Match required".

I have tried sync'ing the music library from my PC about 10 times now, same result.

What has iTunes match done to deactivate music I physically own, and how do I make it stop?