"This song is not currently available in your country or region."

I have tens of thousands of songs that I have digitised from vinyl and cassette that I purchased in the US and Europe over the last 30 years or so. I am now a permanent resident of the country of Belize in Central America. I can play ALL these mp3 files just fine from my iTunes on my old MacBook (13-inch, Aluminum, Late 2008), and from my ancient iPod (Classic 5th Generation 30gb Black Model A1136 2006). See MacBook image inserted:

But when I try to play them from my 2016 iPhone SE, after actually loading them onto my phone, random albums and individual tracks off albums or cassettes get the "This song is not..." notification modal. And I do mean "random!" This is one whole album digitised from vinyl that will not play on my iPhone:

And, for instance, one track, "For You Only," is the only track that will not play of off the Alison Moyet album "Alf" (a cassette transfer). The same condition remains regardless of my internet, wifi, SIM, or service provider status and combinations thereof. I have no idea why this is happening or how to fix it. Can anyone suggest what is going on, and how I can enjoy ALL of my music that I paid for? Thanks advance.