Errors "Failed to login - null" or "Failed to login - invalid session" when joining a server

These errors mostly happen when there is a Microsoft account authentication issue on your launcher, whether it is Technic or CurseForge.

Closing the game and launcher completely, logging out from the launcher, and relogging back in are the most common fixes.

If that still doesn't work, you can navigate to %appdata%/roaming/.technic and delete the oauth folder.

If this still doesn't resolve the issue, you can open a support ticket on our Discord server.