Has anyone experienced this error with trying to run this mod?

" [gmDoom] lua/doom/hooks.lua:30: attempt to perform arithmetic on field 'TICRATE' (a nil value) 1. v - lua/doom/hooks.lua:30 2. unknown - lua/includes/modules/hook.lua:84 " (without quotes)

I have everything properly installed (the Doom2.wad file is in the proper directory) and I cant spawn in anything though the menu. The enemies and weapons are listed as icons, but the gmod engine spawns the above error message and I cannot spawn in any related workshop entities.

I used to have an older DooM mod before the steam gmod update. Is it possible if that mod is conflicting with this? (It simply added a few DooM weapons and only the original Cyberdemon)
How can I get this mod up and working?