Issue: the password expiration of the Office 365 global administrator account will cause Azure AD Connect and DirSync to stop synchronizing on-prem AD to Office 365 Azure AD.
Prevention: One solution is to exclude your Office 365 global admin account from password policies and set it’s password to never expire. Note: Always have a very strong password on your Office 365 global admin account.
- launch an instance of Office 365 PowerShell connected to your tenant
- Run the following command:
Set-MsolUser -UserPrincipalName email@example.com -PasswordNeverExpires $true