This is a common error that occurs when the user is trying to run a 'stale' book. Meaning, the book is in the user's inventory, but the mod's code isn't on the server. And/or the user is missing a main()function. That's a necessary entry/starting point for the mod. When the user runs the mod book, our server is told to look for a main() function.
Here are some thing you can do to reload the code:
- First ensure you are connected; if you're connected, on the main homepage you'll see 'server status: online'
- Press the mod button for that mod. Look for the yellow text in Minecraft that states "mod loaded (mod_name)"
- Try making a small, meaningless edit to the code, such as a variable assignment. Then press the mod button again.
- Make sure your mod has a main function in its code
- Make sure the word main is in all lowercase letters
- Try downloading a smaller-sized Minecraft world from the LearnToMod homepage.
If you've tried those things and it's still not working, let support know at firstname.lastname@example.org