I purchased DLC (Hearthfire & Dragonborn) today from Amazon. Plugged in the activation codes and Skyrim updated itself. When I look under DLC for Skyrim it shows both are there as "Retail" purchases.
However, my DLC mods will not work (BOSS says DLC is not installed) and looking at the Steam store says I do not own the DLC. Googled for help in figuring out what happened but not coming up with anything useful.
EDIT: Verified cache and found an issue. It's now downloading an update - fingers crossed.