Priority Inbox won't load any mails

I’m running Mail version 2.2.4 on Nextcloud version 25.0.3 on Docker.
My issue is that when I launch the Mail App it does not load any mail in Priority Inbox or All Inboxes, but loads perfectly if I click on each Inbox account separately.

I have two IMAP-accounts that work fine but not in those scenarios. And as a result the Mail Widget on the Dashboard doeas not sload any mails either.

Is this a known Issue or Do I have to configure something?