This is caused by RetainPro being unable to contact our activation server. Verify that you have an Internet connection. Check your firewall and anti-virus software to verify that www.enercalc.com and www.mykron.com and www.retainpro.com are permitted/trusted. Use the ping command at the Windows command prompt to determine the current IP addresses for these URLs if needed.
Finally, if you use a Proxy server, you can enter your Proxy server settings by clicking License > Software Activation > Specify Proxy Server.