letsencrypt_certificate RuntimeError: [gitlab.xxxx] Validation failed, unable to request certificate

ERROR while starting gitlab: letsencrypt_certificate[gitlab.xxx.xxx] (letsencrypt::http_authorizat ion line 5) had an error: RuntimeError: acme_certificate[staging] (/opt/gitlab/e mbedded/cookbooks/cache/cookbooks/letsencrypt/resources/certificate.rb line 25) had an error: RuntimeError: ruby_block[create certificate for gitlab.xxx.xxx] (/opt/gitlab/embedded/cookbooks/cache/cookbooks/acme/resources/certific ate.rb line 108) had an error: RuntimeError: [gitlab.xxx.xxx] Validation failed, unable to request certificate

The above error in gitlab is usually due to firewall issues at client side. To resolve do the following:

1. Open firewall for 80 443
2. Configure dns for the gitlab url
3. Do port forwarding if necessary in your local firewall