Login to webpage in a dashboard

Hello. I have a problem with a portainer page docked in a dashboard. When I open the dashboard it prompts me to login page. I fill credentials but the portainer replies with “unable to login”.
This happens only if I reach the dashboard using the fritz box uri, like: http://raspberry.xxxx.myfritz.net:8123/dashboard-portainer/0.

I’m able to login if I reach the page from local network: