New Error Code H31 - Misdirected Request
Change effective on 27 April 2021
We’ve added a new error code: H31 Misdirected Request. The error is emitted when Heroku receives a request for an app at the wrong endpoint (IP address). The client will receive a HTTP 421 Misdirected Request response. This can happen because the client is using stale DNS information, or the client is accessing the app through a CDN that has stale DNS information. Verify that DNS is correctly configured for your app. If a CDN is configured for the app, consider contacting your CDN provider.
See the error code documentation for details.
The error code for Misdirected Request was previously H30 but that was found to conflict with an existing Heroku-internal error.