SSO authentication handler not working

[joe_s66]

I'm trying to set up SSO authentication on 6.2 on a dev author instance for the NTLM set. I have configured the Header Names property in the Adobe Granite SSO Authentication Handler as 'LOGON_USER'. The 'path' is set as / and the ID format set to ^corp\\(.+)$

When I logout of the instance and try to reload the page, I get the login page.

I also see this message in the error.log:

08.03.2017 15:10:58.406 *WARN* [127.0.0.1 [1489003858397] GET /libs/granite/core/content/login.html HTTP/1.1] libs.granite.core.components.login.login$jsp j_reason param value 'unknown' cannot be mapped to a valid reason message: ignoring

Thanks for any assistance.