Failback means returning a package in FAILOVER state to normal activity.
To do this, the original source server of the package has to be available and activated. If the source server has suffered problems that led to formatting the server, make sure to name the server and the SQL server instance with the same names. That way, you will be able to reuse the license number for the HotDBWAN server activation.

Click on the package node in the packages list and click on "Failback" in the "Packages" menu.

The failback operation first re-creates the original source database using the primary target database backup. Meanwhile, users may continue working as usual. After the source database is restored, you will be asked to make sure no one is using the primary target database.

Then, the failback operation finishes the original database restore without losing any last changes made on the primary target database. Any further changes on the primary target database will be lost.

After the original source database is restored, it returns to function as the package source. Then you will be notified that it's ready for use.