hundreds of albums missing from "Purchased" in iTunes store

I have purchased hundreds of albums from the iTunes store, going back to October 2005. I have a personal account (k**@***.***) that has been active for that whole time and that I've used for most of the purchases, which is part of a family account owned by my spouse (c***@***.***). In system settings on our iMac, I see:

but in the Music app (logged in using my k*** account), in iTunes Store > Purchased, it says "This iTunes account is not set up to use Family Sharing. Learn More." and only 15 albums are listed, all purchased since 2020. This is a problem because I still have 455 old DRM-encumbered files that I'd like to update using iTunes Match, but they don't show up in my purchase history. I've gone through the steps on the linked Learn More page, without success.