You are supporting a customer-facing authentication flow for a benefits platform. Employees normally click the Castlight Single Sign-On entry point, get redirected to their identity provider, and return to the app with a valid session. A client reports that users can no longer log in through SSO, and the issue is affecting a live rollout. You need to identify where the failure is happening before making any changes.
A client reports that employees cannot log in through Single Sign-On. What are the first three things you would check?