Why is domain mapping going to main site and not the subsite?

I have the domain mapping plugin installed, which has worked very well to this point. The problem is that on the latest attempt to map a domain, it is just pointing to the main site.

The domain of the subsite is : http://adunumfitness.com

I have used and set up multiple other domains with the domain mapping plugin without issue.

Any help would be greatly appreciated.