Domain mapping stopped working!

This was working fine for one fo the sites installed with wp multisite, we had an issue with sitemap.xml not working so we through to change the domian filed on DOMAIN.COM/wp-admin/network/site-info.php?id=XX page . it was to that didnt work, after that we changes it back to . now the domaing mapping has stoped working for this particular domain, rest of them work but this prticule one is not mapping at all. All DNS settings are the same as before but we keep getting “Domain name is unavailable to access.” though nothings changed at the DNS level at all!