"This item is not currently available in your country or region" message when trying to play tracks on my IOS devices

Very many of the music tracks I have copied from CDs or I have bought and downloaded from recognised music and audio drama websites will no longer play on my iPhone 14 Pro, iPad Mini 5 nor my iPad 9, all up-to-date, running IOS 18.7.1! Like many other 'sufferers', I am FURIOUS about this, having spent many, many hours compiling many favourite playlists to enjoy offline when travelling, etc. All of the 'affected'/missing tracks remain readily playable on my MacBook Air (running Sequoia 15.7.1). Having tried to resolve this problem through online research, I discovered that this issue has affected many Apple Music users (whether or not they are paying subscribers) over several years, but no definitive solution has yet been found.

I have tried many of the suggested actions (un-Sync all playlists. sign out & sign in again, re-Sync playlists, unload/reload Music app, etc., etc.) with no joy. Another factor is that some of the tracks still remain playable on my iPads, but not on my iPhone; I daren't Sync my iPads again until this issue has been resolved, otherwise I may very well lose those tracks, as well!

The only tracks that are fully 'available' on all devices are those which I bought from Apply Music years ago. I have never changed my Country/Region and users have said that licensing is not the issue.

PLEASE, Apple Music - ANYONE - give us a cure for this immensely frustrating situation!!!