Troubleshoot password synchronization
Some users can't sign in to Office 365, Azure, or Microsoft Intune In this scenario, passwords of most users appear to be syncing. However, there are some users whose passwords appear not to sync. The following are scenarios in which a user cannot sign in to a Microsoft cloud service such as Office 365, Azure, or Intune. They include information about how to troubleshoot each scenario.
Scenario 1: The "User must change password at next logon" check box is selected for the user's account To resolve this issue, follow these steps:
1. Do one of the following:
In the user account properties in Active Directory Users and Computers, clear the User must change password at next logon check box.
Have the user change their on-premises user account password.
2. Wait a few minutes for the change to sync between the on-premises Active Directory Domain Services (AD DS) and Azure AD.
References:
https://support.microsoft.com/en-us/help/2855271/how-to-troubleshoot-password-synchronization-when-using-an-azure-ad-sy