apple ID verification of old apple ID

I'm constantly receiving a popup on my iPhone XS and Apple Watch 4 (Cell) asking "Apple ID Verification". Problem is, this Apple ID was with an old work email address that I left over 10 yrs ago, and I have not had the popup in that 10 yrs until last week.

It is NOT popping up on my MacBook Air.

I acknowledge there may be some purchase of music or music loaded from a PC when I was using the old Apple ID all that time ago, however I can't find that to remove it.

Anyone know why after 10yrs this would start appearing?

I have wiped the Watch and setup as new. I have not doe that to the phone yet though.