'MISSING CONTENT' Issue (I can't play anything!)

Hi Folks,
I’ve been getting this super frustrating issue recently:
I have a disc copy of TMCC, I own a 1st gen Xbox One.
I’ve installed the disc and downloaded the Campaign+Multiplayer for Reach, 3 & 4. (with both keys for Reach & ODST downloaded too).

EVERY time I try to launch anything, MP or Campaigns (from Reach, 3 or 4), the game insists that the content is not installed, when it is installed.
I’ve checked the content screen, tried restarting the game, restarting the console, redownloading everything, nothing has worked so far.
This is one of the most frustrating glitches/issues in my entire gaming experience!

Thanks for taking the time, hope you can help,
Take care,
L.J.