Direct answer
Your world/chunk was opened by a newer Minecraft version than the server you are trying to run now. Paper does not support downgrading worlds. Restore a backup from before the upgrade or run a server version new enough to read the upgraded data.
Why it happens even if nobody played
Loading the world in a newer server can upgrade saved data automatically. You do not need to explore or modify a chunk manually for its data version to become newer than an older server expects.
Safest recovery choices
- Stop the server and copy the current folder as a forensic backup.
- If you have a pre-upgrade backup, restore it to a separate test directory and run the old version there.
- If no old backup exists, return to the newer server version that can read the world and continue from there.
Do not force Paper to ignore the world data version
Paper documents -DPaper.ignoreWorldDataVersion=true but explicitly warns that it is highly unrecommended, unsupported, and may permanently corrupt the world.
Plan future downgrades before upgrading
Take a full world/server backup before changing Minecraft versions. Keep that backup untouched until you are certain the upgraded server, plugins, datapacks, and world all behave correctly.
- If a newer Minecraft release saved the world, installing an older server JAR is not a safe rollback. Region and entity formats may have been upgraded.
- Keep the newer-version world untouched, identify the last compatible pre-upgrade snapshot, and restore that snapshot into a separate test directory.
- After recovery, check player data, advancements, dimensions and plugin world references before returning players to the restored server.
Official references
These references were checked while preparing this fix. Version-specific behavior can change, so use the project documentation for your exact release when a detail differs.
Related fixes and guides
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