Between 2:19 PM and 05:30 PM PST on Mar 12th, the Smartsheet Admin Center was inaccessible. Customers attempting to access were redirected to the legacy admin experience. We traced the root cause to an expired internal certificate, and renewed the affected certificate to address the issue.
There was a failure in our internal expiration checking system that caused this to be missed. We are making improvements based on our learnings from the incident to avoid similar incidents in the future.