Use XM360 to ensure the DLC is showing as "Uncut/Unlocked" so the game recognizes them immediately.
The Zombie Island of Dr. Ned , Mad Moxxi's Underdome Riot , The Secret Armory of General Knoxx , and Claptrap's New Robot Revolution . Borderlands [Jtag/RGH DLC]
It’s designed to be clear, helpful, and organized. Use XM360 to ensure the DLC is showing