Can't select calendar, notpossible notworking errors

A few days ago my calendar located here: http://bgmellinger.com/schedule-service-apt/ stopped working. I ruled out any plugin or theme conflicting using my staging site on WP Engine: http://bgmellinger.staging.wpengine.com/schedule-service-apt/. Any ideas how I can get this working?

I'm running the latest version of WordPress and Appointments+.