Please proceed through these troubleshooting steps to ensure everything is configured properly:
Check your DNS settings for both your primary domain and any mapped domains. The A Records should match exactly.
Ensure that you have configured your mapped domain as an Alias Domain or Addon Domain in your server configuration settings (cPanel, etc).
Double check your mapping settings in the Domain Mapping System plugin settings area.
If you find that your mapped domain is redirecting to your primary site domain or you are getting an insecure website warning in your browser, please attempt the following:
Clear cache at all levels, including Server, Website, CDN, and Browser, and then open the website in an incognito window to test if it continues.
Ensure you have SSL set up properly for all domains. Run a test by accessing your site via "http" and "https" in the URL. Sometimes the SSL certificate may not be configured properly, causing a redirect on the secure version, and perhaps not the insecure version.
If you find that your mapped domain is not showing your primary site and your DNS settings are properly configured, it indicates a server misconfiguration:
Ensure that your domain is set up as an Alias Domain.
Ensure there is not a second website installation for your mapped domain and delete any "extra" root directories specifically set up for the mapped domain. All domains should be rooted to the primary site's WordPress installation. Be careful not to delete the primary website folder, and always ensure you have a site backup before deleting anything.
Contact your hosting company to check if the configuration settings are stored properly for your Alias Domain. Ask them: "I want to ensure that my Alias Domain is properly rooted to my primary domain website folder. Is there anything that would be preventing this from happening on my server?"
After making any kind of change whatsoever, it's important to ensure you clear the cache at all levels (server, website, CDN, and browser), or altogether disable caching while configuring Domain Mapping System.
Once you have things working again, you can always re-enable it, and you should not have any issues keeping it enabled.
If the troubleshooting steps above don't help, please kindly contact our support by opening a ticket above.