THIS IS HOW TO FIX IT WHEN AN IPHONE CONNECTS TO A MICROSOFT EXCHANGE SERVER BUT WON’T SYNC

1. Login to your Domain Controller using domain admin credentials
2. Go into  Active Directory Users & Computers
3. Click View, and make sure Advanced Features is enabled.
4. Now, right-click on the user with the issue and select Properties.
5. Go to Security and then click Advanced.
6. Click Add, choose “Exchange Servers“, and then click OK.
7. In the Applies to box, click Descendant msExchActiveSyncDevices objects. (make sure to choose the correct object because they’re a lot of similarly named choices)
8. Under Permissions, click and enable Modify Permissions.
9. Click OK three times to get back to AD.

As long as the smartphone was already connected to ActiveSync the syncing should start almost instantaneously, you shouldn’t need to reboot or re-setup the account.