Updating/editing Jira issue with REST API with variable URI using VBA

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I've modified Fabiano's solution here to create Jira issues in Excel/VBA for the rows selected in a spreadsheet; it worked out well and I was able to create issues from Excel just fine.

Now I want to be able to modify the issues in Excel. So I tried the following, but it seems like it is not even accessing the URI. As you can see, the URI is varying each time because every row has different Jira issue information (for example, row 2 is for TEST-111, row 3 is for TEST-112, ....)   

Sub updateIssue()

    Dim id As String
    Dim rng As Range
    Dim rs As Long

    Dim JiraService As New MSXML2.XMLHTTP60
    
    Dim ResponseTxt As Variant
    Dim Summary As Variant
    Dim Description As Variant
    Dim Project As Variant
    Dim IssueType As Variant
    Dim IssueData As Variant
    Dim Path As Variant
    Dim UN As Variant
    Dim PW As Variant
    Dim Assignee As Variant
    Dim sEncbase64Auth As Variant
    Dim IssueKey As Variant
    Dim IssueAddress As Variant
    Dim IssueURL As Variant
    
    
    
    UN = Sheet2.Range("A4").Value
    Pw = Sheet2.Range("A5").Value
            
    For Each rng In Selection.Rows
        rs = rng.Row
    
        Summary = ActiveSheet.Cells(rs, 4).Value    'summary
        Description = ActiveSheet.Cells(rs, 5).Value     'Description
        IssueType = ActiveSheet.Cells(rs, 9).Value      'IssueType
        Assignee = ActiveSheet.Cells(rs, 8).Value     'assignee
        IssueKey = ActiveSheet.Cells(rs, 14).Value     'issue key# in the format of TEST-111
        IssueAddress = """ + "https://your-domain.atlassian.net/jira/rest/api/latest/issue/" + IssueKey + """
                 
        IssueData = " { ""update"": {}, ""fields"" : { ""parent"" : { ""key"" : ""TEST"" }, ""summary"" : """ & _
                Summary & """, ""description"" : """ & Description & """, , ""assignee"" : { ""name"" : """ & Assignee & """ }} } "
          
        sEncbase64Auth = CommonFunction.EncodeBase64(UN & ":" & Pw)

        ActiveSheet.Range("G6").Value = IssueData & " | Auth Basic: " & sEncbase64Auth

    'Updating/editing issue     
        With JiraService
            .Open "POST", IssueAddress, False
            .SetRequestHeader "Content-Type", "application/json"
            .SetRequestHeader "Accept", "application/json"
            .SetRequestHeader "X-Atlassian-Token", "nocheck"
            .SetRequestHeader "Authorization", "Basic " & sEncbase64Auth
            .Send (IssueData)
            ResponseTxt = .ResponseText

            
        End With
        
        ActiveSheet.Cells(rs, 8).Value = ResponseTxt
         

        Set JiraService = Nothing
        
    Next

End Sub

' Module CommonFunction
Public Function EncodeBase64(text As String) As String
    Dim arrData() As Byte
    arrData = StrConv(text, vbFromUnicode)
 
    Dim objXML As MSXML2.DOMDocument
    Dim objNode As MSXML2.IXMLDOMElement
 
    Set objXML = New MSXML2.DOMDocument
    Set objNode = objXML.createElement("b64")
 
    objNode.DataType = "bin.base64"
    objNode.nodeTypedValue = arrData
    EncodeBase64 = objNode.text
 
    Set objNode = Nothing
    Set objXML = Nothing
End Function

I think the parsing part is where it's causing the error, as I do not see ResponseTxt returning anything. How can I solve this?