root@nginx:/etc/nginx/conf.d# certbot certonly --webroot -w /var/www/letsencrypt/ -d pokx.app.ivoice.online
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator webroot, Installer None
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for pokx.app.ivoice.online
Using the webroot path /var/www/letsencrypt for all unmatched domains.
Waiting for verification...
Cleaning up challenges
Running post-hook command: systemctl restart nginx
Failed authorization procedure. pokx.app.ivoice.online (http-01): urn:ietf:params:acme:error:connection :: The server could not connect to the client to verify the domain :: dns :: DNS problem: NXDOMAIN looking up A for pokx.app.ivoice.online

IMPORTANT NOTES:
 - The following errors were reported by the server:

   Domain: pokx.app.ivoice.online
   Type:   connection
   Detail: dns :: DNS problem: NXDOMAIN looking up A for
   pokx.app.ivoice.online

   To fix these errors, please make sure that your domain name was
   entered correctly and the DNS A/AAAA record(s) for that domain
   contain(s) the right IP address. Additionally, please check that
   your computer has a publicly routable IP address and that no
   firewalls are preventing the server from communicating with the
   client. If you're using the webroot plugin, you should also verify
   that you are serving files from the webroot path you provided.