Hybrid Environment: Microsoft Server 2019, Microsoft 365, Azure Active Directory.
Initial start-up Microsoft 365 users added on-prem server OS Server 2019 and connected to Azure services. Server 2019 no boot and reinstalled the OS, ADDS. Now when trying to add on-prem users receive a sync error for duplicate attribute UserPrincipalName, and an additional user is created. Could someone please guide me on how to resolve sync errors in Azure AD Connect and Microsoft 365 Admin center when adding users back to the on-prem server?