A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
You can check the various error codes for the Start-SPOTenantRename cmdlet here: https://learn.microsoft.com/en-us/troubleshoot/sharepoint/administration/errors-when-renaming
In this case, it looks like you're getting a temporary/transient error, so retrying after a while should hopefully fix the issue. If that is not the case, best open a support request via the admin portal.