Mods working in single only

My friend and I have been downloading some mods but can’t seem to get them to work on a Listen server. Some work and some Don’t, but I would say 80% of them do not work over listen. And yes they have been extracted and Installed properly in all their Designated folders. Everything is fine in a single player game but nothing at all appears in a Multiplayer. Most recently Tried was:

Dans Npc Pack
Huge Drivable Cars
Neo Heavy Combine

Do “NPC”,“Drivable Vehicle” And “Model” addons work on a Listen server or Dedicated only? Or is there something that must be done to have it work on a Listen server?

Thanks

Make sure script enforcer is off.

Thank you very much for that, it all seems to be working now, and something so SImple Lol