I play Walking Dead via Steam on Mac. I can't play 400 Days. Steam tells me that I've already bought the DLC. Episode Status shows "Special Episode" is installed. The background for it is red versus the dark tan of the others. When I play my current game (ended at the conclusion of episode 5 before 400 Days was released), I am shuffled through the different episode load screens until I am stopped on "Special Episode". There is no option to play the episode. I can go back to Episode 5 and play.
How exactly do I play 400 Days? Should I continue from Episode 5? I don't have an option to reinstall the DLC.