Licenses are always valid for more devices. You should see your Internet Security license in your linceses list. To use the license on your new device, just open Avast on the new device, go to the Account section, login with the login details, that you have your licenses. You should immediately see the available licenses with the "Use license" button. Just click the button and Avast should start to upgrade to this license automatically.
We will check, why your current device mistakenly states wrong license.