emails stopped receiving

Hi Experts
One of my user has stopped receiving emails on his mobile.

When i look into mailbox features below are the settings

Mobile Devices
Disable Exchange ActiveSync
Enable OWA for Devices

When i look into MobileDevie Details

I can see the Mobile deivice of that mobile as Access Granted

Removed the account on mobile and recreated it works fine but would like to know what could be the reason for this.