Issue symptoms
One of the agents can't access Zendesk and encounters a blank white screen when trying to log in. When I review the browser console, I see the error ERR_CERT_DATE_INVALID.
Resolution steps
Ask the agent to check whether the date and time settings on their device are correct. Incorrect date and time settings on a machine can cause SSL certificates to throw errors, such as ERR_CERT_DATE_INVALID.
For more information, see this article: Security resources for Zendesk Support.