jcoffey-dev is traveling from Thursday 1 October through Sunday 4 October. Issues and pull requests are welcome, and will get an answer after that. Thanks for your patience.
When a valid certificate already covered a domain's names (one stored
by hand before the domain was switched to automatic, for instance), the
renewal task ended with NotDue, which the task manager treats as a
permanent failure. Nothing rescheduled it, so the certificate expired
unrenewed. The renewal now returns a new AcmeRenewal task due when the
certificate falls due, the same way a successful renewal does, and logs
it as a backoff.
The ACME integration suite checks that renewing again right after
issuance hands back one AcmeRenewal for that domain, due at the
certificate's renewal point.
jcoffey-dev