- Confirm server and clients use the same Project Zomboid build.
- Verify the Workshop page supports that build and multiplayer, and install every required item.
- In host settings, check both the Steam Workshop selection and the active Mods selection. On a dedicated server, compare
WorkshopItemswithMods. - Restart and let the server finish downloading before anyone connects.
- Read the server startup log for “not found,” a missing dependency, or a Mod ID that never loads.
- Test one mod on a new server world, then add the remaining set in batches.
Identify where the failure lives
- Works in single-player, absent from server log: server configuration is incomplete.
- Present in server log, client gets a mismatch: client and server Workshop copies differ.
- Loads but one feature fails only online: confirm the author supports multiplayer and inspect the feature-specific trace.
- Server stops with the mod enabled: isolate dependencies and conflicts on a new world.
Sources
The Indie Stone support: Build 42 hosted server not loading mods — Official Build 42 support case.
Build 42 multiplayer mods discussion — Community-confirmed dual-list fix.
Steam multiplayer mod discussion — Historical community troubleshooting.