Songs are suddenly grayed out on iPhone

Hi all,

It seems like suddenly hundreds of songs in my Music Library are grayed out on my iPhone. Mostly, they appear to be songs I ripped from CDs many years ago. When I tap on the song on the iPhone, I get a message that says "The item is not synced across your devices. On your Mac or PC, go to Apple Music . . . and select Sync Library." These songs have been playable from my phone for many years. I recently updated to iOS 18.5.

The songs exist and are playable on my MacBook (actually on an outboard hard drive). I've tried to Sync Library from the MacBook, but that didn't seem to do anything. I'm unable to drag and drop the songs from the MacBook to the iPhone when the iPhone is plugged into the MacBook. (That should work but it doesn't!).

Did the "manually manage music" option disappear?

If anyone has any experience along these lines or ideas, I'd appreciate it. I don't have the CDs anymore and can't re-rip them (and would hate to have to do that, anyway).

Thank you.