I got a "device not communicating" error from my WWN devices - since other posts here made it sound like a simple re-auth might not always help, I contacted support.
They determined that it wasn't authorized with Nest, so I re-authed, and that seemed to fix it.
It occurs to me that it's almost exactly a year since I added WWN to vera. Does that correspond to an expiry time in the auth token?
If so it would be nice if the plugin could tell us (it does sound like the API should return an explicit "expired" status).