Your Project Zomboid server could not load its world

The notice The server could not load its world on the Game Settings page means that on its last start the game refused the world and shut down. The world was saved by a newer version of the game than the build your server now runs, and an older build cannot open it. The world itself is unharmed.

How it happens

You moved Beta Branch to an older build than the one the world was played on, for example to Build 42 pinned (42.19) after the world was saved on a newer release. The panel warns Switch to an older build? before this: How to choose Build 41 or Build 42 for your Project Zomboid server.

Play the world again

1. Open Settings, then Game Settings.
2. Set Beta Branch back to the newer branch the world was played on, for example Build 42 (current).
3. Restart the server. If Steam Auto Update is off, use Update now so the build installs: How to update your Project Zomboid server.
4. Check the Console for SERVER STARTED and your world: How to check which world your Project Zomboid server loaded.

Stay on the older build instead

Change Server Name. That starts a new world and keeps the old one for when you switch back: How to switch between Project Zomboid worlds on your server.

Build 41 and Build 42

A Build 41 world never loads on Build 42, and the other way round. There is no conversion. See How to keep a Build 41 world and a Build 42 world on one server.

If you do not know what the world was played on, restore a backup from before the change: How to restore your Project Zomboid world from a backup, or open a ticket.