Help - Domain mapped site is redirected to signup page

I just attempted to domain map one of our subsites. As I went to check whether it is now mapped - what comes up rather than the site is the signup.php form to create a new site under that domain!!!!!!!!

Also, I went to check to see what might be different in the other domain mapped sites configuration. The configuration is the same but now I see that each of these other successfully mapped sites has a "Needs Revalidation" under health status with direction to refresh health status. However it doesn't say how to do the revalidation. Is this revalidation process something that needs to be done frequently. Should there be a notification that a revalidation is needed?