I created a subdomain and it is giving me an error message that a DNS record of it already exists, but it doesn't exist. The subdomain is nowhere to be found.
Do you have root access to this server? If so, check the DNS zone of the domain name and ensure there are no "A" records already added for this subdomain. You can have your hosting provider assist you with this task if you do not have root access or the ability to use the Advanced DNS Zone Editor in cPanel.