Root Cause
This issue had the same root cause as the incident that occurred after it in the US east region. Please view that link for a better understanding of the root cause, technical details, monitoring and mitigations.
Timeline
2026-02-20 19:00 UTC – Isolated customer reports came in of no sip responses to invites
2026-02-20 20:34 UTC – Looking at various customer examples, we figured out that the common factor in problematic calls was the chicago based SIP loadbalancer.
2026-02-20 21:26 UTC – SIP in Chicago was drained after ensuring it there was enough capacity in other regions.