Extensions are stored in a different table. So you will need to use a bit different approach:
# retrieve extensions associated with the request in the DB$e= Get-CertificationAuthority -ComputerName "xxx" | Get-DatabaseRow -Table Extension -RowID xx | ?{$_.ExtensionName -eq"2.5.29.17"} $asn= New-Object System.Security.Cryptography.AsnEncodedData @(,([convert]::frombase64string($e.ExtensionRawValue))) $ext= New-Object System.Security.Cryptography.X509Certificates.X509SubjectAlternativeNamesExtension $asn,0