The Kenilworth release saw the introduction of using Google credentials on the SSL login page.
This article provides guidance for what to do when the Google button "doesn't work".
You can click the Google Sign-In button, but nothing happens the user is not authenticated, cannot get past the SSL or non-SSL login page, and cannot browse to the Internet.
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Your Name's not on the List, You're not coming in
If there's a mismatch between:
... this would leave users' credentials being rejected as they would be seen as coming from an unauthorized source.
Are you Certified for Smoothwall?
You must install the HTTPS certificate (downloaded from Services > Authentication > Google > Chromebook settings section) to all network devices used generally speaking you can use something similar to a Group Policy Object (for Active Directory networks) or an Administration Console (for Google networks) to push out the certificate to all devices.
Are you still Inspecting Google?