Appointments+ Calendar "Next Month" button not working

Appointments+ Version 2.1.0

Test Case: Appointments+ Calendar "Next Month >>" button not working

Steps:
1) Appointments Settings -> click Create an Appointment Page with current month's schedule
2) Navigate to generated page: /make-an-appointment
3) Click "Next Month >>" button

Expected behavior: Clicking button will show the schedule for the next month
Actual behavior: Nothing happens

Example site: see Support Access comments for example subsite.