Error 404 item string in frame widget habpanel


I have a problem with showing an item string inside a frame widget. It is independent which item string I used. Every time there is an error 404 inside the widget. The notification shows HTTP ERROR 404 Problem accessing /habpanel/FRITZ!Box%207430. Reason: Not Found
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Can somebody explain me the problem? I have no idea. The address shows the right value of the string: Fritz!Box 7430.

Thank you for your help.

Greetings johannes