Plugin only authenticating Admin level user with windows HttpWebRequest .NET

Hi all, we’re using this plugin on a WPEngine build. We have followed the install steps, we can get it to authorize and return a token with a cURL command, but when we run it through our desktop app, which uses an HttpWebRequest (a .NET API), it only works when the user level is admin, otherwise it returns a 403 and no token. As an admin, it authorizes and works.

We’re not sure if we need to pass extra header information with the call, or reconfigure the .htaccess. Any help would be appreciated.