I believe I've followed the docs, but am getting a 400 status code when trying to get an access token. I've created the API code and call the following URL to get the auth code: // https://api.cc.email/v3/idfed?client_id=22c<redacted>2c3b&redirect_uri=https%3A%2F%2Flocalhost&response_type=code&scope=account_read+account_update+contact_data private HashMap< String , String > headersMap = new HashMap<>(); public static void main( String[] args ) throws IOException { ConstantContactUtilities constantContactUtilities = new ConstantContactUtilities(); constantContactUtilities.getAuthCodeFromAccessTokenAndRefreshToken(); } public ConstantContactUtilities() { // apiKey and clientId are the same field. Stupid ConstantContact uses both terms for the same thing String apiKey = "22c<redacted>2c3b"; String clientSecret = "RPd<redacted>jCQ"; String credentials = apiKey + ":" + clientSecret; String authorization = "Basic " + Base64.getEncoder().encodeToString(credentials.getBytes()); headersMap.put( "Authorization" , authorization ); } public void getAuthCodeFromAccessTokenAndRefreshToken() throws IOException { String authCode = "Bo090<redacted>8NQAEt"; HttpUtilities httpUtilities = HttpUtilities.getInstance(); String url = "https://idfed.constantcontact.com/as/token.oauth2?code=" + authCode + "&redirect_uri=https://localhost&grant_type=authorization_code"; HttpResponse httpResponse = httpUtilities.doPost( url , headersMap , new HashMap< String , String >() ); System.out.println( httpResponse.getStatusLine() ); <-- 400 status code } } What am I doing wrong?   ... View more