A note for others in case someone finds it useful.
A few days ago, all my Z-wave devices spontaneously became unreachable. Eventually I realised this pointed to the Z-stick being at fault, so I tried...
...triggering a network optimisation (didn't work - no devices found)
...reloading the interface in Indigo (didn't work)
...unplugging/replugging the Z-stick (didn't work)
...updating Indigo to 7.3.1 (didn't work)
...rebooting the MacMini (didn't work)
At this point, I was convinced my Z-stick had died and I would have to rebuild the network with a new stick
But I thought I'd try one more thing with the Gen2 Z-stick, to create a new network with a spare device. So I entered exclusion mode using Indigo, triggered 'exclude' on the device, and to my surprise, I got an exclusion message in the event log. There was life in my stick!
Next try was inclusion mode, and that worked too.
Tried sync device - that worked too. Lots of neighbours found
Ran a full network optimisation - that also worked
And like magic, my whole network is back. Happy days!
So the process of excluding & re-including a device was enough to get the stick out of whatever mess it was in, and back to normal