Exchange calendar events show as tentative even after clicking accept on mobile devices

A user would receive and accept meeting invites on his phone. Then he would go on his PC and click the meeting in the calendar to read the details. Then, back on the phone the meeting would move from accepted to tentative.

1. Log into OWA as the user, then go to the options > See all options
2. Select settings in the left menu, the choose calendar
3. Then on the right side of this window, deselect “Automatically place new meeting requests on my calendar, marked Tentative.”
4. Save this change/exit

Test this by having another user send an invite for a meeting, accept it on the device then go into the users calendar and click the meeting. The meeting on the phone should stay as accepted now.