Synchronization of music across all devices

The problem turned out to be the shared library from my old Mac Pro. Devices in our house that had sync'ed to that library kept a stale copy of the library and refused to update to just using the Apple Music library until I completely removed all sharing and existing music on my iPhone. My laptop came upright as soon as I uploaded the old house music archive onto its desktop Thunderbolt disk array but the iPhone was still holding the stale playlist pointers to the offline server. After I had removed all music and sharing references from the iPhone it was able to start from scratch and sync'ed to the new library on the laptop as well as Apple Music.

Nice to know the solution since I have a Mac Studio on order to replace the MBP as my desktop machine and it will be taking over the Thunderbolt disk array along with the music library and I will see the same scenario with the Home Sharing library pointers on the devices (2 laptops, 2 iPads, 2 iPhones, and 3 Apple TVs) all over again.

That doesn't fix things - but as I did this I note that the content that is not being sync'ed is specific to some albums things I had in my master CD library on an old Mac Pro I recently retired. I assumed that I didn't need to keep that library online when I shut that machine down.

The problem in playing this album is replicated in my MacBook Pro and the songs show up grayed out and will not download or play.

I am going to try moving that library onto one of my MBP disks and see if this has somehow confused Apple Music. The old Mac Pro (2010) got left behind when iTunes got replaced by Apple Music.

That's my working theory right now. I am 233GB into copying 450+GB of my old iTunes Library disk onto one of the drives in a Thunderbolt drive array connected to my MBP and will then point Apple Music to it to sync that library. All of my other computers, iPads, and iPhones were correctly configured for doing the Apple Music Sync but prior to us using Apple Music we had shared music on the devices tied to the old Mac Pro which acted as the house music server. We did still have the old Mac Pro online when we first moved over to Apple Music on the rest of our devices but the library was stuck on the iTunes archive. The problem I am having seems to be specifically tied to music that was in that archive and known to the rest our devices in the house.

I am being told by Apple Music on my iPhone that it cannot play the selected music until I go to my Mac and Sync the Library. Not just once - every time I try to select new music.