Check the Minecraft generation
The official project says Minecraft 1.17 and newer require Clumps on the server side; older versions require it on both sides. Confirm your exact game version before applying that rule.
Find the machine running the world
For a hosted multiplayer world, identify the server instance and its mods folder. For singleplayer, use your own game's active instance. A launcher profile and a hosting panel may point to different directories, so record which one you changed.
Plan a simple verification
Restart the affected instance and review startup output. Ask a player to perform a familiar XP collection task while you observe the server. Keep the test small and record the installed file name. For an older multiplayer setup, document the matching client files as well so everyone uses a consistent configuration. Our Client / Server page provides a quick reference while you prepare the installation.
Next step: read the installation guide or find a matching download.
Project reference: Official Clumps project and file details.