Problem restoring calendar events

I have four sections of the same course. I created a number of calendar events in one  of them and did a backup, with the option to include the calendar events selected. But when I then restore  that backup in another section the events don't appear.

I made sure at all times to check all the boxes about calendar events. Also, I did the same thing six month ago and it worked fine.

I did some looking around and it says that this might take some time. But it has been 12 hours, and the calendar events are still not there.