Hi Neil,

Thanks for your answer.

I believe it's just the way the POSTMAN console outputs the headers.

Good news is that we finally got it working. After playing a bit with %Net.HttpRequest class we created a utility test class method -  below - where we stopped using the ..Adapter.PostURL() method of the adapter class and called the Post() method of the http request class. We played a bit with the parameters in the header and voila!  we were able to move past the authorization stage:

ClassMethod CallDocmanAPI(pURL As %String, pToken As %String) As %Status
{
Set pOutput=$$$NULLOREF
Set tAdapter = ##class(EnsLib.HTTP.OutboundAdapter).%New()
set tStream = ..TestJsonReader()
W !,tStream.Read(tStream.Size)
do tStream.Rewind()
W !,"URL : "_pURL
Set pResponse = ##class(UCLH.SIP.Test.REST.DocmanResponse).%New()
#dim tHttpRequest As %Net.HttpRequest
#dim tHttpResponse As %Net.HttpResponse
set tHttpRequest = ##class(%Net.HttpRequest).%New()
set tHttpRequest.ContentType="application/json"
set tHttpRequest.ContentCharset="UTF-8"
set tHttpRequest.FollowRedirect=1
Set tHttpRequest.Https=1
Set tHttpRequest.Port=443
set tSC = tHttpRequest.SetHeader("content-type", "application/json")
set tSC = tHttpRequest.SetHeader("accept","*/*")
set tSC = tHttpRequest.SetHeader("authorization","Bearer "_pToken)
set tSC = tHttpRequest.SetHeader("host","api-demo.docmansandpit.com")
set tSC = tHttpRequest.SetHeader("accept-encoding","gzip, deflate")
set tSC = tHttpRequest.SetHeader("cache-control","no-cache")
set tHttpRequest.SSLConfiguration="TestDocman" 
set tSC = tHttpRequest.EntityBody.CopyFrom(tStream)
W !,"HTTP HEADER: ",!,tHttpRequest.ReturnHeaders()
try {
Set tSC=tHttpRequest.Post(pURL,2,1)
Throw:$$$ISERR(tSC) ##class(%Exception.StatusException).CreateFromStatus(tSC)
}
catch (ex) {
Set tSC = ex.AsStatus()
W !,$System.Status.GetErrorCodes(tSC)_" : "_$System.Status.GetErrorText(tSC)
Quit 
}
Quit tSC
}

Kind Regards.