I was following this tutorial to install a SSL certificate to my website: How To Secure Nginx with Let’s Encrypt on Ubuntu 18.04.
When I ran the following command:

sudo certbot --nginx -d woodcraftgallery.com.np -d www.woodcraftgallery.com.np

The following error came up:

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

   Domain: woodcraftgallery.com.np
   Type:   connection
   Detail: dns :: DNS problem: SERVFAIL looking up A for
   woodcraftgallery.com.np

   Domain: www.woodcraftgallery.com.np
   Type:   connection
   Detail: dns :: DNS problem: SERVFAIL looking up A for
   www.woodcraftgallery.com.np

   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.

I have the following domain set up:

The IP address is correctly assigned and the HTTP seems to be working fine. I have configured the firewall just as said in the tutorial. Please tell me how I can resolve this issue?