License problem

Code:

Your license could not be activated because:
Invalid License File..

   1. First, go to http://verify.cpanel.net/ and enter the public IP address of this server to make sure it is licensed.
   2. If licensed, try running /usr/local/cpanel/cpkeyclt from the command line as root.
   3. You'll also need to make sure that port 80 is open to contact our license server and that your hostname is a FQDN.

it turn out like this..again and again.. i type hostname xxxx.mydomain.com and /usr/local/cpanel/cpkeyclt ...after that i can use my whm but it come back after 5-6hrs.. i need to fix again and again.. what should i do?