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 autenticationauthentication issue on your Launcher,launcher, whether it is Technic or CurseForge.
Closing the game and launcher completely, logging out from the launcherlauncher, and relogging back wouldin beare the most common fixes,fixes. but ifIf that still doesn't work, you can accessnavigate 'to %appdata%/roaming/.technic'technic and delete the 'oauth'oauth folder.
If this still doesn't solveresolve it,the issue, you can open a support ticket on our Discord server.