You plan to use Password Sync on your DirSync Server with Azure Active Directory {Azure AD) on
your company network. You configure the DirSync server and complete an initial synchronization
of the users. Several remote users are unable to log in to Office 365. You discover multiple event
log entries for “Event ID 611 Password synchronization failed for domain.” You need to resolve the
password synchronization issue. Which two actions should you perform? Each correct answer
presents part of the solution.

A.
Restart Azure AD Sync Service.

B.
Run the Set-FullPasswordSync Power Shell cmdlet.

C.
Force a manual synchronization on the DirSync server.

D.
Add the DirSync service account to the Schema Admins domain group.

Explanation:
Changed from AB to BC.
http://jermsmit.com/office-365-initiate-a-full-password-sync-using-dirsync-jermsmit/
https://jaapwesselius.com/2014/07/28/force-dirsync-to-synchronize-with-office-365/
A)
Not Correct, Azure AD Sync or AADSync is the new version of DirSync.