Steam won't let me buy Sims 3 University Life because I "don't have" the Sims 3 on their client

[76561198168009374]

Your transaction failed because you are trying to buy 'The Sims 3: University Life' which requires ownership of 'The Sims™ 3'. Please correct the error and try again.

Problem is I own a physical copy of The Sims 3 but it won't let me add it, and they are taking forever to add it, and when I tried to enter the product code that came with the disk it rejected it for not being a Steam product code. I am not buying The Sims 3 again just to buy that expansion pack. Help!

[Pheace]

The Sims 3 expansion packs on Steam will only work with the base game on Steam.

If you don't want to rebuy then activate your key on Origin and buy the expansion on there.

[eram]

You cant add the sims3 retail on steam. It's an origin game.

[TirithRR]

Not all retail games can be activated on Steam. If you don't own the game on Steam, you can't buy the DLC on Steam.

I think the Retail version of Sims 3 can be handled on EA's Origin client, and you can probably buy the DLC there.