Hello,
To activate a new NIC or network card, start the Zentyal GUI administrator application.
Select Network
Select interfaces
The Name of the new NIC or network card ( eth0 or p1p1 , depending on the card ) is now showed in the field "Name"
Select "Method" and select then DHCP or Static
Click on the tab "CHANGE"
Select now Gateways and add the new gateway of your network ( if necessery )
Now the networking is working with the new network card or NIC
Best regards,
Ian