The issue is that the key files aren’t created inside the webroot folder.
OS: CentOS 6.7
Command Line: # ./letsencrypt-auto certonly --webroot -w /home/USERNAME/public_html -d DOMAINNAME.COM
Failed authorization procedure. DOMAIN.com (http-01): urn:acme:error:unauthorized :: The client lacks sufficient authorization :: Invalid response from http://DOMAIN.com/.well-known/acme-challenge/pnZ6e6CK4x7IL5r_bIUGfnd36Zp4Yo4W1IlpqdN_Vpo [xx.xx.xx.xx]: 404 IMPORTANT NOTES: - The following errors were reported by the server: Domain: DOMAIN.com Type: unauthorized Detail: Invalid response from http://DOMAIN.com/.well-known/acme- challenge/pnZ6e6CK4x7IL5r_bIUGfnd36Zp4Yo4W1IlpqdN_Vpo [xx.xx.xx.xx]: 404 To fix these errors, please make sure that your domain name was entered correctly and the DNS A record(s) for that domain contain(s) the right IP address.
Debug Log (Verbose -vvvv): http://pastebin.com/vBGv9tac
Note: Replaced domain name with DOMAIN, username with USERNAME, IP with xx.xx.xx.xx.