Fixing the error "Failed to find the 'domain' function" while issuing an SSL certificate from the Let's Encrypt

Symptoms

Issuing of an SSL certificate from the Let's Encrypt failed and the error "Failed to find the 'domain' function" appears.

Causes

The name server is not installed within the ispmanager 6 control panel.

Solution

Install the DNS server in "Settings" - "Software configuration" - "Name server (DNS)" section.

See our documentation about name server installation for more details.