'Missing property: clientId' in the ManagePermissionGrant.ps1 PS script

[Cianod]

When i run the script, you can see it outputs the $grantParams object and the clientId is in there.
Any idea why it would then throw a 'Missing property: clientId' error on the New-MgOauth2PermissionGrant command?
I have global admin rights on this tenant.

thanks