An error occurred executing Configuring AAD Sync task: System.InvalidOperationException: Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly Style to display a notification fro a service application.
Enabling Conditional Access for all users breaks azure ad sync connect as the service account used by the application couldn’t authenticate with Multi factor authentication.
usually the default service account starts with Sync_Servername_
Excluded the specified Azure AD Connect service account from Conditional Access.