I have a navmesh generated for the map, it covers all walkable ground and so on. The issue is, when I launch the gamemode, the zombies don't move, even with a navmesh.

I generated the navmesh using the command Nav_mark_walkable and then Nav_generate. I try to save it to NZombies, and get this error:

[nZombies Unlimited [v1.0]] lua/nzombies-unlimited/core/entities_tools/naveditor.lua:76: Tried to use a NULL CNavArea!
1. GetID - [C]:-1
2. savenavmeshtable - lua/nzombies-unlimited/core/entities_tools/naveditor.lua:76
3. func - lua/nzombies-unlimited/core/entities_tools/naveditor.lua:89
4. unknown - lua/includes/extensions/net.lua:33

What can I do to fix this? do I need to delete the zombie spawnpoints and replace them since they were there before the navmesh, do I need to install another addon...?