auth_id is never found.

[mbalsam]

This line in GoogleAlertAPI::TryLogin() always returns empty string.

auth_id = json[3].ToString();

Any ideas?

[ThijsvanL]

The reason this happens is because the session is not logged in :
The auth_id and auth_token are pulled from a complex nesting of arrays in javascript in the google alerts page. If the session accessing this page is not logged in with a google account, the json[3] field will be empty.
If you use 'view page source' on a logged in google alerts page, you can find the array structure by searching for 'window.STATE'.