I have a client beginning to use CRM on desktop computers to arrange Appointments for customer service visits.  The Appointments save as such. 

The customer service reps in the field access these Appointments from CRM Mobile (through the iPhone web browser).  They can the Appointments under My CRM on the Calendar.  However, when they click on these Appointments, they open as Tasks. 

Instead of the "Date/Time" and "End Time" fields that were set on the desktop as an Appointment... they see the "Due Date/Time" and "Start Date/Time" of a Task. 

The "Date/Time" (of the appointment) appears in the "Due Date/Time" field (of the task), and "End Time" shows in "Start Date/Time."  That in itself is backwards.

Worse, it prevents the mobile user from saving the record, because you cannot have a due date ahead of a start time.  If they reverse the times in order to complete the Save, the record is transformed from an Appointment to a Task, which can then be confirmed on the desktop or the mobile.

What could possibly be causing these Appointments to appear as Tasks on the mobile device?

This is just about to go live and hadn't happened in earlier testing.  This is CRM 2018 R2.

Please help!  Thanks very much...

Kevin