What DLC might you be referring to? While you did indeed migrate your Battle.net data over to Steam, you stopped playing the game before Forsaken was released, so it seems unlikely that you would have purchased that expansion from Blizzard. If you’re referring to the year one content, Red War, Curse of Osiris, and Warmind; those campaigns were removed from the game, along with some of the related locations. You do not have cross-save active at this time, or I would ask if you were perhaps expecting your purchased expansions to transfer from console to PC, or vice versa. Content is license bound to the platform on which it was purchased, and cannot be transferred between platforms.