Mapping Domain not working on some of my domains

Since November I have been able to map about 80 domains on my Wordpress MU site. For some reason the following domains just do not want to map.

All the settings on each domain are exactly like the rest of the domains which have been mapped successfully on the same site. I have triple checked all their settings and cannot figure out why this is happening.

Can someone please assist and let me know what is wrong here?