to add to the question above:
If I open the event in IE, then it says the event can’t appear in a frame, and asks me to open it in a new window. It will let me do that.
If I open an event in either Chrome or Mozilla (I use Mozilla as my default browser), the page blanks out (goes dark) and a pop-up appears but nothing appears in it and it is translucent. I can close it and it goes back to the page.
The webpage where the calendar appears (currently as a widget) is https://www.telg.com.au/register (events are in February)
This error occurs in both widget form and as a full calendar.
I’ve tried to clear cookies and browser history on all browsers to see if that helps, but it doesn’t.