Everest Install Issues

There are a number of ways that installing Everest or mods can go wrong, and this page aims to help with those issues. At the top is an install checklist, with short points to ensure the highest chance of installing on the first try. After that is a list of the most common error messages, along with the fixes for them and their explanations.

Note: We are unable to support pirated copies of Celeste due to not knowing what modifications may have already been made to the game. You are unlikely to get help fixing your copy if it does not work.

Everest Install Checklist

• Celeste is installed with the latest version (1.4.0.0) available
• Celeste was launched at least once since installing
• Celeste is not open while installing
• Olympus is up to date
• You have read/write permissions for your Celeste install folder

Error Messages

MonoModRules failed resolving Microsoft.Xna.Framework.Game

Make sure to run Celeste at least once before trying to install Everest. The Windows XNA version of the game requires the XNA library, which is retrieved on first launch. If it has not yet been retrieved, Everest fails to install.

The process cannot access the file '...' because it is being used by another process.

Celeste was running while you tried to install Everest, or some other mod. Close the game fully, then try installing again.

This can also be caused by programs like OneDrive or Google Drive Desktop scanning the files.

Unsupported version of Celeste

Your Celeste install is outdated, update it. As of the writing of this page, the most recent version of Celeste is 1.4.0.0.

Many of the modifications that Everest makes to Celeste only work on the latest version, and since trying to maintain compatibility with multiple versions is a nightmare, it was decided to only support the latest version.

This error can also trigger if you have a pirated copy of Celeste - see the top of this page for more info.

Ionic.Zip.BadCrcException

Something went wrong while downloading a mod, and one of your mod zips got corrupted, requiring a reinstall.

If you have an idea of which one it may be (if you downloaded one recently, or if you can check your log.txt for the last loaded mod), then delete it from your Mods folder and redownload it.

System.UnauthorizedAccessException: Access to the path '...' is denied.

Everest needs permission to make changes to your Celeste install, and that means you need permission to make changes. Please see this third-party article for help: https://www.thewindowsclub.com/change-files-and-folders-permissions-in-windows-10

Unexpected version of MonoMod patcher

Update Olympus. There should be a red ❗ on the Options and Updates panel when there’s an update, which you can then open and press Install.

Still not working?

Should you still have trouble with installing Everest, please join the Celeste Discord 🔗 and upload the Olympus log-sharp file to the #modding_help channel.