subdomain issue

I created a new subdomain using the control panel
version, 0.29.15

I have manually restarted apache

domain names are just examples listed below

subdomain.domain.com does not work
www.subdomain.domain.com works correctly

This is the apachehcp_subdomains.conf

ServerName subdomain.domain.com
ServerAlias www.subdomain.domain.com
UseCanonicalName Off

How do I fix this?

Thank you