Hello,
response time of the Avast's support is I'm afraid a matter of days. This should be solved by organisation changes but it will take some time.
The SecureLine VPN client asks the system daemon to start/stop the VPN connection. The API unfortunately doesn't provide any error, therefore the client displays only a general error message "VPN connection cannot be established". If the VPN connection fails, it would be helpful to create a support package from the application's Help menu - it is a zip file containing the daemon's log (com.apple.networkextension.log), basic network diagnostics, application log, product configuration (including license identifiers) and relevant OS informations.
Regarding the product activation, there's no limitation imposed by design.
Best regards,
Martin