Compatibility Issue with Sims Medieval on my Mac

I purchased "The Sims Medieval Deluxe Pack". I successfully downloaded "The Sims Medieval" and "The Sims Medieval: Pirates and Nobles". I was able to install "The Sims Medieval" but when I try to install "The Sims Medieval: Pirates and Nobles" I get an error. 

The error text reads:  "The version of The Sims Medieval™ installed is not updatable and is not compatible with The Sims Medieval™ Pirates and Nobles."

Any help would be very appreciated.