We don't want to return an X509 Cert from a PKCS12 data blob
I can confirm that this specific error message in this case is just noise and not indicative of an actual error.
The majority of actual error logging for AD CS Connector requests will be in the
com.jamfsoftware.jss.objects.pki.adcs package. If you enable debug logging for this package (or globally) then you should be able to see detailed logging of the request/response around Jamf Pro and AD CS Connector communication. Any unrecoverable errors are logged at the error level by default.
If Jamf Pro and the AD CS Connector are able to communicate then you should be able to see an error message returned by the AS CS Connector with a reason code that begins with "CR_DISP". If you don't see anything like that then there may be an issue with how the connection between Jamf Pro and the AD CS Connector is configured.