‘This song is not currently available in your country or region’

I moved to the UK 7 years ago. Songs I bought on iTunes on a iPhone whilst living in Australia used to all play okay. Since upgrading to iPhone 14 I have noticed many songs now are greyed out & say ‘This song is not currently available in your country or region’.

I bought these songs - I should be able to play them wherever I live.

This isn’t fair - how do I fix this?