Welcome to the forum! I've found other forum members to be very helpful in finding solutions to issues with the calendar and other lds.org applications... however, it is easier to help when more details are provided
Let us know as many specifics as you can, for example, are you clicking the event and selecting the Delete button from the pop-up, or are you selecting the
Edit event details & location link from the pop-up and then deleting it from the Event Details page? When you change the event, what specifically are you changing, like the description, name, location? What internet browser are you using (sometimes errors or problems can be specific to a browser)? What is your current calling (which can sometimes help determine what permissions you may or may not have on the calendars website)?
Hopefully with a few more details someone else using the forums can help you figure out what other steps you might take for the problem you are seeing.