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 the following are permitted/trusted:
enercalc.net (without the www.)
Use the ping command at the Windows command prompt to determine the current IP addresses for these URLs if needed.
It's possible that internet activation is being prevented due to security software or hardware (like a firewall) blocking our software's ability to connect with enercalc.net via HTTPS REST API calls.
Finally, if you use a Proxy server, you can enter your Proxy server settings by clicking License > Software Activation > Specify Proxy Server.