Remove an On-Prem Firewall Management Center from CDO
Use the following procedure to remove an on-prem management center and it's registered devices from CDO:
In the navigation pane, click.
Ensure the FMC tab is selected and choose the on-prem management center you want to remove.
In the Device Actions pane located to the right, click Remove On-Prem FMC and its managed devices.
Click OK to confirm that you want to remove the on-prem management center and its managed devices from your tenant.
Refresh your browser to see an updated list of available devices.