"We have detected that your firewall is preventing the connection to our server"

Q: When I tried to install the aircraft, I got the above error message, Could you help me?

A: If you receive this error while installing, indicates that the installer cannot reach the server for verification of the serial.
Some systems add the Carenado server to a blocked list when it's identified as a threat.
To correct or avoid this, check the file "hosts" located in the folder C:\Windows\System32\drivers\etc and open it using a text editor and check if there's any Carenado line in there?

Probably at the bottom of the file you'll find one or two lines like this: 
127.0.0.1 securecarenado.com
127.0.0.1 www.securecarenado.com
Just delete that lines, save the file, and try installing again, this should solve the issue.