model kits that dont work

i recently bought gmod and some of the model kits dont work.

Left 4 Dead Content
GMOW-v3 Cars pack 1-3

and yes i read all the readmes and installed them in the correct place

How do they not work?

the vehicals i can only get through browse window and they arnt driveable

  1. those are not model kits, they are addons
  2. they are insanely old

where can i ask about oddons then which forum i mean