New version breaks subdomain login

We are using the CAS option of Authorizer to provide a single sign-on to several WordPress sites. The previous release of Authorizer was working on our MultiSite with a subdomain.domain.ext and subsub.subdomain.domain.ext type home URLs.

We noticed today that we are not able to log in to the subsub.subdomain.domain.ext site. As soon as we click the button to begin single sign-on, the CAS login service gives a “403 – Forbidden: Access is denied” error that was not happening prior to the update. I see the plugin auto-updated Tuesday, so it coincides with the login issue.

What steps can we take to troubleshoot and get CAS working on the “sub subdomain” again? Would it be helpful to update Core?