Appointment 1.3 - fatal error issue with adding Locations

Fatal error: Class 'AgmMapModel' not found in /home/troy/public_html/clients/ on line 151

Hello, this is the php error I get on screen after adding an address in the new "Locations" tab feature. Exact steps are: Settings - Locations tab - Add location - In create a new location box - paste in address - add - blank screen with above error.