HTTP Error 52 Empty reply from server

I am using HTTP client with 509 certificate and cookies auth. Driver is CURL code to send HL7 messages to McKesson.  Cloverleaf proc log shows connection established and message post, but the vendor states they do not see data posting.  I confirmed with our network team and theirs that they see traffic when the post is sent from us to them.

In Cloverleaf, error capture is showing Cloverleaf protocol error encountered is httpc_query error 52, empty reply from server.

Has anyone else connected successfully to McKesson using HTTP client?

Vendor cannot provide logs or errors because they state they are not receiving the message post.  Could this be an issue on our side and if so is there a way I can capture more details of the transmission?   I have verbose on but from what I can see in the log the message has been sent.