Google Calendar on XIBO

when I set google calendar with secret Ical url it does’t show the events of the calendar.
The schedule is shown blank. I use the calendar widget.
What could be the reason?

Did you tried to add this google calender with a different app?

Yes, I can see that calendar with curl.
Could it be that I need a special permission for the calendar widget? I’m not an admin user at Xibo.