Music purchased by me cannot be streamed using iCloud Music

Music that I purchased through iTunes plays ok on 1 computer, but on another, I get a message "cannot be downloaded because it was not purchased with your Apple ID".

I have authorised both computers with the same Apple ID but a few years ago when MobileMe was merging with Apple ID, I opted not to merge the 2 accounts but the email address associated with the account changed. Some music has the old email address while other music was purchased using a new email address.

Now here is the sticking point: some songs in an album will play while others show the message above. I can download the tracks that won't play and then they will play while other will stream ok.

Does anyone have any ideas on how I can fix this?

Using iTunes 12.2 with iCloud Music enabled, iTunes Match is OFF

MacBook Pro 2014 running Yosemite

MacMini 2008 running Yosemite