Refresh rate on Appointments+

Our client isn't seeing events they enter on google calendar syncing with the calendar on the website, resulting in double bookings.

Yes, the setting for the google calendar are set to the A+ <-> GCal (Synchronization).

When we manually go in the backend of the WP site and resync the calendar it works, but I thought the plugin refreshed at a certain interval.

Thanks in advance for guidance on this.