You may need to set up a wildcard subdomain, and this can be done within your cPanel account. A wildcard DNS record is a record that matches requests for non-existent domain names. A wildcard DNS record is specififed by using the * symbol to create a record for the *.yourdomain.com. The most common applications for a wildcard subdomain is for use with SSL or WordPress MU.
Creating a Wildcard Subdomain
First, log into your cPanel account and under the "Domains" section select "Subdomains"
Next, in the first open field, place a * symbol there signifying that you are creating a wildcard subdomain and click "Create".
Congratulations! You have now successfully set up your account for wildcard domains. You still may need to modify your .htaccess file. However, if you have set up wildcard subdomains for WordPress Multisite, it will automatically configure the .htaccess file for you.
Please check the next article on Modify an Add-on domain's document root in cPanel. If you missed our previous article, please see the Setting up a Redirect for a Domain in your cPanel tutorial. For more information on this course please visit Managing your Domains in cPanel.