Depends on your client. What are you using?

I was having this issue I think.  Clicking on specific notes did nothing.  I refreshed the whole page and then they started working again.

It's possible that the event you're trying to view is private or has been deleted. In order to view the event, you'll need to make sure you have the correct access levels and permissions. If you continue to have trouble viewing the event, you may need to contact the event organizer to get access.