Microsoft Azure recently released clear road map of Azure Data sync. It replaces the SQL data sync service in classic portal.
If any of the customers are using SQL Data Sync then they need to migrate those sync groups to new portal.
Following the announcement, Azure classic portal not allowing us to create sync and even the SQL databases also. Microsoft Azure team trying to migrate all the services to new portal and in one point of time, Microsoft will remove the classic portal.
As like the previous service, this migrated service also still in preview.