Getting this specific trace error when using "only" AAAA (IPv6) record.
Attempting to renew cert from /etc/letsencrypt/renewal/domain.com.conf produced an unexpected error: Failed authorization procedure. domain.com (http-01): urn:acme:error:connection :: The server could not connect to the client to verify the domain :: Fetching http://domain.com/.well-known/acme-challenge/PcYcSaZ-junMDR6DmVrCO8Ku4fWgIR4hOc0fpp0_NGY: Error getting validation data. Skipping.
The command used was
# certbot --authenticator standalone --installer apache
But the command above was producing this error when trying to challenge the server, don't exactly know why (suspect IPv6 only machine)
To correct this error, just make sure apache is working and serving pages on port 80 and run command bellow ...
# certbot certonly --webroot -w /home/user1/public_html/