Do I need a dedicated IP for the multisite installation for Domain Mapping to work?

Domain Mapping isn't working. I've also tried the recommendations from with the plugin. I am on a shared hosting service and the domain for my WP Multisite network is not the root domain (it's an add-on). Is this what is causing the problem? Any help would be greatly appreciated.

WPMU: LevitateCreative.com

Domain I'm trying to map: imburton.com