Domain mapping

I have a multisite install in a adddon folder... called 814media.com my main domain on the cpanel is fanpage4me.com

I installed the domain mapping plugin on 814media.com... then I added a site jb40th.com to point to the server ip

Instead of jb40th resolving to 814media.com it resolves to fanpage4me.com and does not keep the url jb40th.com... It switched over to fanpage4me.com

Is there a way to make this work