The lemmy.world instance was just updated to version 0.18.2. The login issues that were being reported (for example, here) are now resolved.
For release notes: https://lemmy.world/post/1339018
Edit for those who still have issues logging in:
- When using a browser: clear cookies and cache
- When using an app: remove your lemmy.world account and add it again.
If you’re still having issues just try logging in and out again.
I’m not now, but I was wondering if the update may have logged people out to help with that, or if that may have just been a coincidence.