Linear switches can be kind of a bitch to pair. I have 14 of them, and recently did a panel swap; so I’ve done quite alot of pairing.
For the best success, the switch needs to be very close to the panel when you pair it. You need to take the switch to the panel or visa versa. For new switches that I’ve not installed yet, I cut the end off of a computer power cord (pig tail) and then use wire nuts to temporary wire the switch so I can plug it in right next to the panel. If your switch is already wired, then it’s easiest to take the panel to the switch. To do this, open the panel up and disconnect the power while the Go Panel is on and booted up, then it will run on battery.
Once the panel and switch are about 6" apart, put the panel in zwave discovery (zwave->add device). Then click the bottom of the switch twice, then the top twice: down down, up up. Do this then wait a few seconds, then repeat until the switch pairs. If it still doesn’t pair, then you’ll need to reset the switch. The linear dimmers have a pullout tab next to the LED. Pull it out then push it back in to reset.
This should do the trick.