Follow these steps if you can see the DLC abilities, but not the maps.
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Follow these steps posted by a dev, Crispy. Note that not all of the files he asks you to delete may be there. In my case I only had zzzdlcenglish000.sdmd2 and zzzdlcenglish000.sdpk2.
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Rename your steam ClientRegistry.blop file, detailed here.
After relaunching Steam the DLC maps will begin to download.