They seem to have had some success working on this, but it appears that once again, you will need to follow the old routine:

1. go to Settings > Accounts
2. optional (see update below) -- long press on each lemmy.world account to remove it.
3. then add it back again.

[Update: user feedback is that you can just add your existing account again without deleting it and the app will do the right thing]

We are looking at a better way of dealing with this. Thanks for bearing with us.