'invalid credentials' without login

Hi,

I'm new to pleroma/soapbox and created a new test installation of soapbox. It worked for some days but now I got the message 'invalid credentials' in the uppper right corner without trying to login.

I have no idea if this is a bug or if I messed up my installation?! Any docs to read for me? I have no idea how to debug this issue.

This message appears only if the user is not logged in.