We have the following error in the console:
Refused to display 'https://calendar.google.com/calendar/embed?wkst=1&bgcolor=%23FFFFFF&color=%…showTz=0&ctz=Europe/Paris&showPrint=0&showDate=0&showNav=0&showCalendars=0' in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'.
Maybe typing error... Cannot reproduce anyware except with an additional space in agenda id.