GMod Maps not starting/loading

Ok, so I just downloaded a few maps from garrysmod.org. I start up Gmod and see that the maps I downloaded were there, but when I clicked to start them (single player) it doesn’t load, it just stays at the menu screen.

I go to console and type in “map_nameofthemapsIdownloaded” and it says “PENDING”

I know I’m a noob, but what is the problem?