July 2017
I am having this same issue.
I bought the Sims 3 + DLC on STEAM back in 2013 or so. I did redeem the games on thesims3.com , like if i go to my profile there I see the games and packs I bought and redeemed.
What had happened was, I got a new computer since the old one with the Sims 3 + DLC died.
On the new rig, I used Origin, I saw my sims 3 game and DLC, the ones i had bought, ready to go and be downloaded!
The game launched and worked awesomely for a few days...then the DLC started vanishing from the launcher and it became unplayable.
So I deleted everything off Origin ( the files and deleted the game from origin)
I got back onto STEAM , redownloaded the sims 3 + DLC and...no luck. The bloody things I paid for and redeemed do not work.
It is basically one DLC making everything such a cluster mess.
I'm waiting for EA to get back to me.