I have a Kwikset 910 keypad/Z-wave lock. It has worked fine. The other day I couldn't unlock it either from the Keypad or from Z-wave. It was like it had totally died. I replaced the batteries but that didn't help. It should have worked via the keypad if nothing else. So I assumed it was history.
I had a Zigbee conversion unit I had bought and never installed. Just for grins I installed the Zigbee module in the lock. And that solved the problem. The keypad, etc. Started working again.
So it would seem if the Z-wave module goes bad it keeps the whole lock from working. Doesn't make sense, but whatever.
Just thought that might be of interest in case someone else ran into the same issue.