Google Calendar Blackscreen on Player

Hello,
I am having issues with the Calendar Widget including Google Calendar.
In the Xibo CMS the preview shows the calendar just fine. On the player site, it only shows a blackscreen. I don’t have any idea, what is going on.
I am using Xibo CMS as Container in Version release-3.1.3 and Player on Linux installed with snap in Version 1.8-R6.
Am I able to debug this in any way? What could go wrong?

EDIT: On Windows Players it’s working fine.