@danb35, thank you for this extended info.
Actually, I did revoke the certificate on both servers… That’s bad, right?
The site was a nightmare to set up and get running, after a really nasty spamvertizing infection. The server changed twice, DNS changed… Maybe I was too frustrated to think clearly?
What I’ve learned is: never revoke a certificate without a genuine reason.
I also learned letsencrypt delete --cert-name example.com does not work on my Ubuntu server. I tried that first, but because I could not get it working I did the revoke.