I figured out what I was doing wrong. Apparently, you now need to go into Marketplace, look under the "My Collection" tab and choose to 'Manage' (I think that was the option) then it will allow you to select or deselect all of the content you own. I realized that none of the new content I had just bought was selected or enabled. I clicked on each one to make sure it had a green checkmark and okay'd the selections. I think I had to re-start? But this time the new DLC's were all there, available and active to use.
I'm on a MacBook (hopped over here since I couldn't find any posts on the Mac forum) - but I want to confirm this solved the problem for me as well.
