HOW TO MANUALLY SYNC AZURE AD CONNECT
By default Azure AD Connect will sync automatically every 30 minutes. There will be a time for some reason you’d need to force sync the directories on your on-premise Active Directory and Azure Active Directory such as a new user, a new distribution group etc. You can force sync the directories synchronization by using PowerShell command. However, you need to install Azure Active Directory PowerShell Module or by connecting to your Office 365 Exchange Online before your can use the command.