New-SPWOPIBinding : Sorry, we have encountered an error and New-SPWOPIBinding has failed.

Hi

This is a tale of 2: Office Online Servers . Both

1. Both Patched with November 2017 PU
2. Both single instance OOS farms created with a self-cert using the same PS script
3. Both working perfectly, until I decided to recreate and re-export the self-cert ( to the respective WFE) . Is was part of diagnosing an issue that needed a firewall change which has now been successfully implemented.
4. Now one of the OOSs gives this error when I try create a SPWOPIbinding

PS C:\New-SPWOPIBinding -ServerName  OOS.mydomain.com
WARNING: The server did not respond. Trying again (attempt 1 of 5).
WARNING: The server did not respond. Trying again (attempt 2 of 5).
WARNING: The server did not respond. Trying again (attempt 3 of 5).
WARNING: The server did not respond. Trying again (attempt 4 of 5).
WARNING: The server did not respond. Trying again (attempt 5 of 5).
New-SPWOPIBinding : Sorry, we have encountered an error and New-SPWOPIBinding has failed. If you are using a 
server configured with HTTP, you must include the -AllowHTTP parameter.
At line:1 char:1
+ New-SPWOPIBinding -ServerName  OOS.mydomain.com
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (Microsoft.Share...tNewWOPIBinding:SPCmdletNewWOPIBinding) [New-S 
   PWOPIBinding], SPCmdletException
    + FullyQualifiedErrorId : Microsoft.SharePoint.PowerShell.SPCmdletNewWOPIBinding

 Recreated the OOS Farm without any issues>

I can validate https://OOS.mydomain.com/hosting/discovery ok

I have checked Port 443 access from the WFE to OOS, also OK

The log location seems a work of fiction!  Any ideas anyone please.