On rare occasions, after installing Bitdefender on a Windows computer, you will receive an error message indicating that the product was unable to connect to the server to complete the activation: “Unable to connect to the server. Sorry, we are unable to connect to the server. Please try again later”. Typically, this error means that a firewall, DNS, or content filtering system on your network or computer prevents communication with the Bitdefender servers and blocks the activation process.
Regardless of the reason why the message appears in your Bitdefender product, uninstall Bitdefender completely then reinstall it to fix it