I ping my site on pingdom.com over here (http://tools.pingdom.com/ping/) and got result invalid host name. then i check my DNS HEALTH and got result as follow
Everything is fine
The name server failed to answer queries sent over TCP. This is probably due to the name server not correctly set up or due to misconfgured filtering in a firewall. It is a rather common misconception that DNS does not need TCP unless they provide zone transfers - perhaps the name server administrator is not aware that TCP usually is a requirement.