WebRequest with Bearer Authorization in VB.NET - vb.net

Question

I would need to send a POST request to a remote server, which requires a Bearer Authorization.
this is my VB.NET code:
Public Shared Function syncAsana() As String
Dim result As String
Try
Dim token As String = "TOKEN"
Dim uri As String = "https://URL/api/1.0/tasks"
Dim postData As String = "assignee=email&notes=TEST_NOTES&name=NOME 1&projects=123985"
Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)
Dim request As WebRequest = WebRequest.Create(uri)
request.Method = "POST"
request.PreAuthenticate = True
request.Headers.Add("Authorization", "Bearer " & token)
request.ContentType = "application/x-www-form-urlencoded"
request.ContentLength = byteArray.Length
Dim dataStream As Stream = request.GetRequestStream()
dataStream.Write(byteArray, 0, byteArray.Length)
dataStream.Close()
Dim response As WebResponse = request.GetResponse()
Using dataStream1 As Stream = response.GetResponseStream()
................
result = responseFromServer
End Using
response.Close()
Catch ex As Exception
result = ex.Message
End Try
Return result
End Function
the problem is that I always get the error The underlying connection was closed: An unexpected error occurred on a receive
the same request made with jquery / ajax or with curl works.
I have tried both from the local server launched by visual studio, and by putting the code on the production server.
could you tell me where i'm wrong?