wjohn, welcome to the forum. These switches are known in the rest of the world as the Aeon Labs inline switch, so you know what to search for in your future travels on the forum.
If the light is on solid then one possibility is that the switch has already been included in another Z-Wave network. All you have to do is force-exclude it first, which will return it to an unpaired state. Put your Vera in “Exclude a device” mode, bring the switch and the Vera near each other, and press the button on the switch. It should flash to indicate success, and then it should start slow-blinking as your working switch did. Now it is ready to include.
Note that you can use any Z-Wave controller to exclude a device, it doesn’t have to be the one that “owns” the device. This is an escape-clause written into the Z-Wave spec specifically to handle cases like yours.
If force-excluding doesn’t work, then it’s DOA (not unusual for this model) and back it’ll have to go.
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