It’s the calendar on the right hand side of this page: http://www.capecommunityservices.org/poolfitness/richard-pool/
When not logged in as an admin it just shows up as grayed out and there being no events. The error message appears above the calendar when logged in though.
Rolled back to an older version, thanks @kris779 and it’s working. Don’t seem to have lost anything either.
I would say hold off on updating for now until the developer can fix this issue.
Does anyone know where I can get a previous version? No luck finding one so far.