Domain Mapping Domain not working when set as primary

I have a site a It's part of a multisite network. I have used this plugin on many sites on different installs and have no issues but this one is baffling me.

When I have the domain set as the secondary domain, it redirects correctly to the multisite subdirectory site. However, when I set the domain as the primary in the plugin settings, it breaks completely.

The extra odd thing is that it seems to work just fine on my own computer but no one else (including my phone) can reach the site when is set as the primary in the plugin settings.

I really need this fixed so your insight is appreciated.