You will not be able to learn, or add a zwave device if it is currently associated with another zwave network.

Zwave devices can only be associated to one zwave network at a time. If say you get a new panel, or you obtain a zwave device second hand, you will need to use the new panel to remove device(s) from the old network, and then add to current network.

Quote Originally Posted by Jay @Suretycam

1.Services
2.Zwave
3. The little wrench in the corner. (You will need your installer code)
4. Remove Devices
5. Perform the steps to “learn” the device into the control panel.
6. You should see a message pop up on the screen that says “A device has been removed from another network.”
7. Once all of your Z-Wave devices are removed from the old network, you will be able to add them to the new network you’re setting up.
8. After you’ve added all the devices to the new network, run a Network Rediscovery.
Source