The most typical reason is one or more firewall programs (Norton, Zone Alarm, Windows Firewall) are blocking access to the Internet. Make sure that all your firewalls allow both our exe and DNA.dll to reach the activation server. If you are accessing the Internet through a Proxy server and you’ve configured the proxy settings, make sure these are valid. If you are not using Internet Explorer as your browser, it may be configured with invalid proxy settings; unchecking the “Use IE proxy configuration” option in the Proxy Settings screen could help resolve the connection issue.
It is also possible that a connection fails because of heavy Internet traffic. The only solution in this case is to wait 15 minutes or more and then repeat the activation procedure.
Lastly, please make sure the activation password you assign is between 4-16 characters. In many cases we've had users enter a very long password which was rejected by the license server.