Troubleshooting

Sometimes things don’t work as expected. Here are some common issues and their solutions. Some of the solutions may require you to inspect the log files. See Common Terms for log file locations.

If you encounter an issue not listed here, consider asking for help in the Modding Discord server or report the problem to the specific mod’s author.

Mod not loading link

Verify that the mod is in Mods folder in the game directory.

If the mod is in the correct folder, check the MelonLoader console/log for any errors related to the mod. If the mod is installed properly, MelonLoader should log a message indicating that the mod has been loaded. If you see an error message, it may indicate that the mod is incompatible with your version of the game or branch.

Mod/Plugin mismatch link

[WARNING] Failed to load Melon ‘…’ from ‘…’: The given Melon is a Plugin and cannot be loaded as a Mod. Make sure it’s in the right folder.

This error indicates that the mod/plugin is in the wrong folder. Mods should be placed in the Mods folder, while plugins should be placed in the Plugins folder. If you see this error, move the mod/plugin to the correct folder and restart the game.

Outdated mod link

If a mod isn’t working, it might not be compatible with your version of the game. Check the mod’s page for any updates or compatibility notes. If the mod is outdated, you may need to update it to a newer version that is compatible with your game version. Errors commonly seen with outdated mods include missing methods or types, which can be identified in the MelonLoader console/log.

HarmonyLib.HarmonyException: Patching exception in method null

System.MissingMethodException: Method not found: ‘…’

IL2CPP/Mono mismatch link

If you are trying to load a mod and it fails with an error related to IL2CPP or Mono, it means that the mod is built for a different scripting backend than the one you are using. The easy way to determine that is to check the mod’s description on the mod page. If it doesn’t specify, you can check the mod’s .dll file name. If it contains IL2CPP, it is an IL2CPP mod, if it contains Mono, it is a Mono mod. If it doesn’t contain either, it might be a mod for the main branch of the game, which is IL2CPP.

This is a common issue, which can be automatically resolved by using a Plugin, such as OTC Loader (Nexus/Thunderstore) or SwapperPlugin (Thunderstore).

To check for yourself, look at the MelonLoader console/log when you start the game. Il2Cpp mods will usually error with ... Version=6.0.0 on Mono, while Mono mods will error with ... Version=0.0.0 on IL2CPP.

Examples of those can be found below.

Could not load file or assembly ‘System.Collections, Version=6.0.0.0, Culture=neutral, PublicKeyToken=…’ or one of its dependencies. link

This error indicates that the mod you’re trying to load was built for IL2CPP, but you’re running the game on Mono branch. You need to switch to IL2CPP branch in Steam properties or find a Mono version of the mod.

Could not load type ‘ScheduleOne.UI.Phone.Delivery.DeliveryShop’ from assembly ‘Assembly-CSharp, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’. link

This error indicates that the mod you’re trying to load was built for Mono, but you’re running the game on IL2CPP branch. You need to switch to Mono branch in Steam properties or find an IL2CPP version of the mod.

MelonLoader fails to start link

If MelonLoader fails to start, check the log files for any errors. See Common Terms for log file locations.

Assembly-CSharp.dll is being used by another process link

[Il2CppAssemblyGenerator] Unhandled exception. System.IO.IOException: The process cannot access the file ‘\cpp2il_out\Assembly-CSharp.dll’ because it is being used by another process.

This error can appear eg. if the game was started twice. The system is trying to access the same file, but a lock hasn’t been released. This can be resolved by either:

• reinstalling MelonLoader (deleting the <game dir>\MelonLoader folder, <game dir>\version.dll and installing MelonLoader again), or
• deleting the <game dir>\MelonLoader\Dependencies\Il2CppAssemblyGenerator\Cpp2IL\cpp2il_out folder

Error Generating Interop Assemblies link

[ERROR] [Il2CppAssemblyGenerator] Error Generating Interop Assemblies!

This error can appear if MelonLoader is unable to generate interop assemblies for the game. This can be resolved by either:

• reinstalling MelonLoader (deleting the <game dir>\MelonLoader folder, <game dir>\version.dll and installing MelonLoader again), or
• deleting the <game dir>\MelonLoader\Dependencies\Il2CppAssemblyGenerator\Cpp2IL\cpp2il_out folder and <game dir>\MelonLoader\Il2CppAssemblies folder