[_raul]

There's more context in this Heroku Changelog https://devcenter.heroku.com/changelog-items/1813

"On Tuesday June 9th 2020 Heroku changed the certificate used for terminating TLS for built-in <appname>.herokuapp.com hostnames from a certificate issued by DigiCert to one issued by Starfield/AWS. This change was rolled back on June 10th because a small subset of Heroku customers had pinned apps to the DigiCert certificate or had apps that could not establish a chain of trust with the new certificate for other reasons.

A new DigiCert-signed certificate will replace the current one before June 22nd (when it expires)."