Converting from V1 to V2

Working in VBA.

The following V1 code works:

Sub DeleteFile(filename As String)
    Dim req As MSXML2.ServerXMLHTTP60
    Dim Result As String
    Dim Pos1 As Integer
    Dim Pos2 As Integer
    Set req = New MSXML2.ServerXMLHTTP60
    req.Open "POST", "https://api.dropboxapi.com/1/fileops/delete?path=" & "/" & filename & "&root=auto", False
    req.setRequestHeader "Authorization", "Bearer ##########"
    req.send
 
    If req.Status = 200 Then
       Debug.Print req.responseText
    Else
       MsgBox req.Status & ": " & req.statusText
       Debug.Print req.responseText
    End If

 

The following conversion to V2 does not work:

Sub DeleteFile2(filename As String)
    Dim req As MSXML2.ServerXMLHTTP60
    Dim Result As String
    Dim Pos1 As Integer
    Dim Pos2 As Integer
    Set req = New MSXML2.ServerXMLHTTP60
    Dim arg As String
    arg = "{""path"": ""/" & filename & """}"
    req.Open "POST", "https://api.dropboxapi.com/2/files/delete", False
    req.setRequestHeader "Authorization", "Bearer ##########"
    req.send (arg)
 
    If req.Status = 200 Then
        Debug.Print req.responseText
    Else
        MsgBox req.Status & ": " & req.statusText
        Debug.Print req.responseText
    End If
End Sub

 The error I get is:

"Error in call to API function "files/delete": This function requires its argument in the HTTP request body, but your request body is empty."

Similar problem implementing other file functions.

Any ideas?