Unable to restore a site collection to its original location

Restoring a site collection to its original location that has been deleted will fail, when you delete the site collection URL.

You can perform the following steps:

1. Perform restore to an alternative location.
2. Select the original SharePoint Server.
3. Enter the new URL parameter in the agent restore configuration dialog and complete the restore process.

For more information, see Perform a Document-Level Restore to the Alternate Location in SharePoint 2010/2013/2016/2019.