Issue
Beginning at 21:39 UTC (17:39 EDT) on July 17, 2020, a CloudFlare incident caused widespread impact to many Internet services and customer applications.
This appears to be materially resolved as of 22:09 UTC (18:09 EDT).
Resolution
Heroku does not use CloudFlare for its services, but customer applications that use CloudFlare for DNS or CDN services may be impacted. In addition, apps that make API calls (client- or server-side) that are hosted on CloudFlare may see a cascading impact.
For details, please see https://www.cloudflarestatus.com/