This is usually caused by your session ID becoming invalid, for example after merging an account or making a change to your email / username / profile URL.
To fix this:
- Right-click on the Start button, and choose "Run" (Windows 8/10/11) or press WINKEY + R
- Type %LOCALAPPDATA%\mod.io\
- Locate the folder with the ID 2475
- Rename the folder to 2475old
- Restart Deep Rock Galactic
Once you restart the game and navigate to the mod menu, you should be able to reauthenticate to mod.io, which should hopefully resolve any conflicts or issues.