Lost access to DLC Maps in Single Player

[Chase Quinnell]

I recently added the last 3 DLCs on Steam that I did not previously own, (none of which included DLC maps, as I had already bought those months ago). When I went to set up a single player game, the DLC maps such as Donut, Continents Plus, Pangea Plus, etc, all seem to have disappeared. I'm only able to select vanilla maps now.

What happened? I do own the Explorer Map Pack, so why have they disappeared?