I'm starting this as a general trouble shooting aid. The Z-Wave terminology calls it Add Node, but since Bluetooth pairing is widely understood, I propose that we just call it pairing.
Each device needs to be paired with a controller. The device cannot be controlled until it has been paired.
I have the most experience with the Z-Stick from Aeon Labs. There are two that are commonly available for $35 to $45. The white one is the latest and that's what I'm using.
Engen has the ability to add a node without removing the Z-Stick from the computer, but for this topic, I'm removing it.
The steps are:
1. Remove the Z-Stick from the computer
2. Walk over to the device you want to pair.
3. Push the button on the Z-stick and begin watching the lights it is flashing.
4. Push the pairing button on the device (or sometimes just turn it on) and watch the lights on the Z-Stick again
If you are successful, the Z-Stick lights will change from flashing slowly to flashing quickly (several times a second) and then turn solid, and a second or two later go back to the slow flashing. That means the pairing worked.
If it doesn't work, try again a few times.
If it still doesn't work, you may need to "initialize" or "reset" the device. The method for this varies a lot. An Internet search will usually work. Amazon reviews have a lot of useful information.
Some devices seem easy to pair. Some aren't.
The Z-Stick remains in the pairing mode until you either press the button again or you insert it into a computer. So you can pair several devices without pushing its button again.
Please feel free to comment or correct what I've said above. Thanks.