Ok i see now that maybe it was not meant to work as a post request script in Certify.
I had to run manualy with -thumbprint.
I changed this line to pull correct thumbprint:
$Windows_SSLCert = Get-ChildItem -Path Cert:\LocalMachine\My | Where-Object {$_.Thumbprint -match $result.ManagedItem.CertificateThumbprintHash};
/J