Well, basically that's my question. I honestly don't know what using mitmproxy results in a successful request.
Here's what I did:
I really don't know what's going on. Why using mitmproxy made it work.
Ok, it think I found out what happened.
Using mitmproxy "cleans" white spaces in my request. That is why I was successfully getting a response from the server.
This was the culprit:
--header "SOAPAction: \"http://myurk.com/soap/queryRequest\" "
Notice the space I have between \" and "? Removing that whitespace got it working. Mitmproxy probably cleaned that out for me.