Try going to
- Steam>Workshop>Your files>Subscribed items>Unsubscribe from all.
- Wipe the mod folder from C:\Program Files (x86)\Steam\steamapps\workshop\content\108600
- Then go to Steam Library> Project zomboid> Properties> Local files> Verify.
- Restart Steam.
- Remove old server leftovers in User/Zomboid/ Server and Saves/Multiplayer.
- Start a new server