how to install letsencrypt ssl certificate in vestacp?

I am using vestacp with nginx and php-fpm. I am trying to get a certificate for my site. I am getting this error. I am trying to do it using this link https://github.com/interbrite/letsencrypt-vesta . I cloned files successfully I cannot create my certificate. please can anyone help me out. Error is:

Failed authorization procedure. skydental.in (http-01): urn:acme:error:unauthorized :: The client lacks sufficient authorization :: The key authorization file from the server did not match this challenge [zxLQ0SjDPtfaVMsqn5PrifOWrCDIH5SDpquhyYRCSPg.cc9euNkfSp2DJIY99UvlLqM_-WgSWBXYC-6rcC9diII] != [zxLQ0SjDPtfaVMsqn5PrifOWrCDIH5SDpquhyYRCSPg.dNihNa_AZKQDTA9gmqCD8mGhLb1icwHtdq4y_Qiv6kk], www.skydental.in (http-01): urn:acme:error:connection :: The server could not connect to the client to verify the domain :: DNS problem: NXDOMAIN looking up A for www.skydental.in

IMPORTANT NOTES:

• The following errors were reported by the server:

Domain: skydental.in Type: unauthorized Detail: The key authorization file from the server did not match this challenge [zxLQ0SjDPtfaVMsqn5PrifOWrCDIH5SDpquhyYRCSPg.cc9euNkfSp2DJIY99UvlLqM_-WgSWBXYC-6rcC9diII] != [zxLQ0SjDPtfaVMsqn5PrifOWrCDIH5SDpquhyYRCSPg.dNihNa_AZKQDTA9gmqCD8mGhLb1icwHtdq4y_Qiv6kk]

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.

• The following errors were reported by the server:

Domain: www.skydental.in Type: connection Detail: DNS problem: NXDOMAIN looking up A for www.skydental.in

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. 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. Let’s Encrypt returned an error status. Aborting.