Hello Peter! Welcome to the forum!
Thank you for reaching out. I have tried to reproduce the issue in multiple ways, but I always get the login prompt followed by a fully working panel. While we do not have any indication of outages in any of our services, this could have been something temporary. Are you still experiencing the same issue?
I see that someone else created a thread with the same topic, but it has since been deleted by the author. Perhaps that could also point towards a temporary outage?
Please verify and get back to me if you are still seeing this issue!