Calendar not working-freezing & not synching

Hello!

I attempt to open Calendar and it states that it is updating calendars. It will sit there for a few minutes, then usually that closes, but never updates any calendars. I'm left with an empty calendar. If I attempt to add something by clicking the "+" sign I also get nothing. My calendar shows no events. I can't see any of my calendars either.

I've attempted the following:

1. Rebooted.
2. All software is current

Appreciate the help.