Do you have a app on Heroku, DNS on Cloudflare and your SSL certificate is automatically managed by Heroku?
I do. And yesterday I received email like this:
Hi, Automated Certificate Management has failed for the following domains: Domain Reason domain.sk www.domain.sk You should be able to find specific information to correct the above noted errors at: https://devcenter.heroku.com/articles/automated-certificate-management#troubleshooting Happy coding, Heroku
Yep, no reason, obviously.
Following the link gave me something useful (as my DNS records were fine):
ACM is not available if your app is behind a CDN such as Cloudflare or Fastly.
So I check my DNS again and I see that I use 'DNS and HTTP proxy (CDN)'.
Setting it do 'DNS only' and running
heroku certs:auto:refresh --app=myapp did the trick.
My certificate is OK and I can set 'DNS and HTTP proxy (CDN)' again.