Appointments + Client Cancellation not reflected in GCal

I ahve the GCal api setup and working correctly. i also have the two-way sync setup in the AP settings. However, when a client clicks the CANCEL link in the confirmation email to cancel their appointment, that cancellation is NOT reflected in the GCal...

The appoinment does delete from the appoinments list in the AP dashboard, but even after doing a manual IMPORT AND UPDATE events, the cancelled even remains in the GCal.

What's gone wrong?
Thanks so mcuh!