How login to Rational Quality Manager from Microsoft Excel VBA application?

Hello!
I need to import some data from IBM Rational Quality Manager (RQM) v6.0.4 to Microsoft Excel. I want to use Reportable API for that. But I can not login to RQM from Excel. I have spent a lot of time, and there's no success!
If in detail, the problem is next. There's a small VBA code:

Public Function jazzLogin_UNIT()
    Call JazzLogin(getFullServerURI, "jts", "jts")
End Function

Public Function JazzLogin(url, userid, password) As Object

    ' User data
    Dim userdata As String
    userdata = "j_username=" & userid & "&" & "j_password=" & password
   
    ' URIs
    Dim requestURI1 As String, requestURI2 As String
    requestURI1 = "https://jazz.server.com:9443/qm/authenticated/identity"
    requestURI2 = "https://jazz.server.com:9443/qm/authenticated/j_security_check"
    requestURI2 = requestURI2 & "?" & userdata

    ' HTTP service object
    Dim httpService1 As New WinHttp.WinHttpRequest, httpService2 As New WinHttp.WinHttpRequest

    ' Check that form-based authetication is used
    httpService1.Open "GET", requestURI1
    httpService1.Option(WinHttpRequestOption_SslErrorIgnoreFlags) = 13056 ' insecure
    httpService1.send
    Debug.Print "[GET]: " & requestURI1
    Debug.Print "[HEADERS 1] " & httpService1.GetAllResponseHeaders()
    Debug.Print "[STATUS 1] " & httpService1.statusText
   
    httpService2.Open "POST", requestURI2
    httpService2.Option(WinHttpRequestOption_SslErrorIgnoreFlags) = 13056
    httpService2.setRequestHeader "Content-Type", "application/x-www-form-urlencoded; charset=utf-8"
    httpService2.send
    Debug.Print "[POST]: " & requestURI2
    Debug.Print "[HEADERS 2] " & httpService2.GetAllResponseHeaders()
    Debug.Print "[STATUS 2] " & httpService2.statusText

    Set JazzLogin = httpService2


End Function

If I execute "jazzLogin_UNIT" procedure then I have next in the console:

[GET]: https://jazz.server.com:9443/qm/authenticated/identity
[HEADERS 1] Cache-Control: no-cache="set-cookie, set-cookie2"
Date: Mon, 18 Sep 2017 19:04:33 GMT
Content-Length: 1982
Content-Type: text/html; charset=UTF-8
Content-Language: en-US
Expires: Thu, 01 Dec 1994 16:00:00 GMT
Set-Cookie: JazzFormAuth=Form; Path=/qm; Secure
X-Powered-By: Servlet/3.0
X-com-ibm-team-repository-web-auth-msg: authrequired


[STATUS 1] OK
[POST]: https://jazz.server.com:9443/qm/authenticated/j_security_check?j_username=jts&j_password=jts
[HEADERS 2] Connection: Close
Date: Mon, 18 Sep 2017 19:04:33 GMT
Content-Length: 757
Content-Type: text/html;UTF-8
Content-Language: en-US
X-Powered-By: Servlet/3.0


[STATUS 2] Bad Request

I understand that VBA isn't very popular amonst the developers who works with Java applications but the code is very primitive. May be somebody could give me an advice where I'm wrong?
It must be mentioned that there's no problem with credentials. I can login with jts/jts both in Jazz authetication form and in curl utility!
Thank you very much in advance!