I've got multiple Lemmy accounts. I wanted to remove an account, so signed out of it.
This resulted in an empty account UI, no three dots to switch to an existing account, I had to close the app and start it again to see the account menu and then select an existing account to get it to work.
You have accounts in the menu? I have to sign in with user and pass every time I want to switch. The only account in the drop down menu is whichever one I'm currently logged into.