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.
I’ve found for both Liftoff and Jeroba that going to the android apps page on my phone and clearing the cache for both of them cleared up some persistent login/logout issues that removing/adding my account didn’t.