Twitter oAuth 1.1 vb.net (401) unauthorized when posting tweet - twitter-oauth

Question

I have spent some time on this and cannot figure out why I cannot post to twitter from my web site. I keep getting 401 unauthorized. I think that I was successfully posting to the 1.1 auth at one point but something changed in the last 6 weeks or so (not in my code, did oauth get stricter?).
Does anyone see anything that could be potentially causing the problem? Is there anything I can add to the code to get more info on why it's failing?
Private Function NewTweet(status As String) As WebResponse
Try
Dim oauth_token = "token" 'access token
Dim oauth_token_secret = "secret" 'acces token secret
Dim oauth_consumer_key = "key" 'consumer key
Dim oauth_consumer_secret = "secret" 'consumer secret
Dim oauth_version As String = "1.0"
Dim oauth_signature_method As String = "HMAC-SHA1"
Dim oauth_nonce = Convert.ToBase64String(New ASCIIEncoding().GetBytes(DateTime.Now.Ticks.ToString(CultureInfo.InvariantCulture)))
Dim timeSpan As TimeSpan = DateTime.UtcNow - New DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc)
Dim oauth_timestamp As String = Convert.ToInt64(timeSpan.TotalSeconds).ToString(CultureInfo.InvariantCulture)
Dim resource_url As String = "https://api.twitter.com/1.1/statuses/update.json"
Dim baseFormat As String = "oauth_consumer_key={0}&oauth_nonce={1}&oauth_signature_method={2}&oauth_timestamp={3}&oauth_token={4}&oauth_version={5}&status={6}"
Dim baseString As String = String.Format(baseFormat, oauth_consumer_key, oauth_nonce, oauth_signature_method, oauth_timestamp, oauth_token, oauth_version, Uri.EscapeDataString(status))
baseString = String.Concat("POST&", Uri.EscapeDataString(resource_url), "&", Uri.EscapeDataString(baseString))
Dim compositeKey As String = String.Concat(Uri.EscapeDataString(oauth_consumer_secret), "&", Uri.EscapeDataString(oauth_token_secret))
Dim oauth_signature As String
Using hasher As New HMACSHA1(ASCIIEncoding.ASCII.GetBytes(compositeKey))
oauth_signature = Convert.ToBase64String(hasher.ComputeHash(ASCIIEncoding.ASCII.GetBytes(baseString)))
End Using
'-------------------------------------------------------
Dim headerFormat = "OAuth " & _
"oauth_consumer_key=""{0}"", " & _
"oauth_nonce=""{1}"", " & _
"oauth_signature=""{2}"", " & _
"oauth_signature_method=""{3}"", " & _
"oauth_timestamp=""{4}"", " & _
"oauth_token=""{5}"", " & _
"oauth_version=""{6}"""
Dim authHeader = String.Format(headerFormat, _
Uri.EscapeDataString(oauth_consumer_key), _
Uri.EscapeDataString(oauth_nonce), _
Uri.EscapeDataString(oauth_signature), _
Uri.EscapeDataString(oauth_signature_method), _
Uri.EscapeDataString(oauth_timestamp), _
Uri.EscapeDataString(oauth_token), _
Uri.EscapeDataString(oauth_version))
'-------------------------------------------------------
Dim postBody As String = "status=" & Uri.EscapeDataString(status)
ServicePointManager.Expect100Continue = False
Dim request As HttpWebRequest = DirectCast(WebRequest.Create(resource_url), HttpWebRequest)
request.Headers.Add("Authorization", authHeader)
request.Method = "POST"
request.ContentType = "application/x-www-form-urlencoded;charset=UTF-8"
Using stream As Stream = request.GetRequestStream()
Dim content As Byte() = ASCIIEncoding.ASCII.GetBytes(postBody)
stream.Write(content, 0, content.Length)
End Using
Dim response As WebResponse = request.GetResponse()
Return response
Catch ex As Exception
Return Nothing
End Try
End Function