Internet Calendar entries are not displayed Version 7.1


I have added an Internet calendar to view via Menu/Extra/Subscribe to Internet Calendar.

This inserted Internet calendar also synchronizes without error message. So the black circle rotates.

With this Internet calendar also the hook is set before the entry.

Nevertheless, the entries are not displayed with this Internet calendar. 

On another PC next to it, everything works perfectly. 

Thus I suppose that it could lie somewhere in the settings of the PC.
Do I still have to release anything in the PC firewall?
Or does this function need full administration rights?

Would be very glad for a hint!