HTTP 406 Error While Logging In To DocuSign API - docusignapi

Question

I have a prototype WinForms application that uses open-source DocuSign.Integrations.Client library. It was working correctly until a couple of days ago. Now every attempt to login results in HTTP 406 error. No code has changed on my side, and my user name and password are valid (verified on https://appdemo.docusign.com). Any help is appreciated!
Below is the raw request with masked credentials:
GET http://demo.docusign.net/restapi/v2/login_information?api_password=true&include_account_id_guid=true
HTTP/1.1 Accept: application/json
Content-Type: application/json
X-DocuSign-Authentication: <DocuSignCredentials><Username>______</Username><Password>______</Password><IntegratorKey>____-________-___-___-___-____________</IntegratorKey></DocuSignCredentials>
Host: demo.docusign.net
Connection: Keep-Alive
In response, I get a 302 redirect:
HTTP/1.1 302 Found
Cache-Control: no-cache
Content-length: 0
Location: https://demo.docusign.net
Connection: close
And then receive a 406 error:
HTTP/1.1 406 Not Acceptable
Content-Type: text/html
Server: Microsoft-IIS/7.5
X-Powered-By: ASP.NET
Date: Sat, 09 May 2015 19:16:52 GMT
Content-Length: 1346
Connection: close

Answer 1

This is incorrect:
http://demo.docusign.net/restapi/v2/login_information?
api_password=true&include_account_id_guid=true
It should use HTTPS, not HTTP in your GET URL call:
https://demo.docusign.net/restapi/v2/login_information?
api_password=true&include_account_id_guid=true
Also your error is actually describes what is wrong
HTTP/1.1 406 Not Acceptable
Your request headers should be this:
Accept: application/json
Content-Type: application/json
X-DocuSign-Authentication: <DocuSignCredentials><Username>______</Username><Password>______</Password><IntegratorKey>____-________-___-___-___-____________</IntegratorKey></DocuSignCredentials>