On Wednesday, November 25, 2020, starting at about 15:00 UTC Yubico became aware of an issue servicing api.yubico.com requests which were routed to YubiCloud's US-East data center. At peak, about 2.5% of requests were receiving error responses. By 17:00 UTC, error rates had fallen to < 0.5% with complete resolution by 19:00 UTC. Only requests sent to the US-East data center were affected; all other data centers were operating normally. A retry of a failed request should have been successful.
The underlying cause was a prolonged outage of services in AWS's US-East1 region. AWS is YubiCloud's Cloud Platform provider. More information on the AWS outage can be found here.
We apologize for any inconvenience the disruption of YubiCloud's service may have caused. Steps are being taken to mitigate the effects of such outages upon our customers in the future.