How do I recover missing Apple Music library and playlists on iPhone and Windows 11?

For years I've had issues, first with iTunes then Apple Music on Windows, starting with Windows 7, now with Windows 11. On my laptop, from time to time, music just disappears. This is music either 1) I purchased on-line or 2) imported from my CD collection. I do not, nor do I want, I subscription to Apple Music. I just want to have my library usable with individual songs/albums I purchase and download as well as the CD's I import.

Yesterday, I found that ALL of my playlists and about 90% of my music is missing from my iPhone Xr running iOS 18.3.1. When I tap the "Library" icon on the iPhone and look for my playlists, I see a message that reads "Subscribe to Apple Music to save music". When I tap "songs", I see I have about 125 songs on my iPhone out of about 1500 that I had a couple of days ago. Huh?

I was more or less OK with limping along and occasionally re-importing a CD or re-downloading a purchased song/album. Any thoughts most appreciated...

[Edited by Moderator]