I've had the calendar plugin installed and it has been working for almost 3 to 4 weeks without any apparent issues. Although it has been a week since the last time that I went to the calendar page, I had taken it for granted the calendar was working. I went to the page and saw that it wasn't being displayed anymore. At first, I thought the lack of a calendar might be because I didn't have any upcoming events scheduled, so I created and updated a test event. The calendar still wasn't being displayed, but the event itself did show up on a list. I'm not sure why it was working flawlessly but now it will not.