Ahhhh this has been driving me mad for a few days now (actually, more like driving my wife mad who then in turn drives me mad...)
I've been trying to debug this one for a few days and just now I am certain my problem is Amazon itself.
Weirdly if in HE I remove or add devices to be exposed to Alexa I get Alexa notifications on my phone that the devices are added or removed.
I tried removing the device I'm having grief with (I only actually use one HE device with Alexa, a virtual switch) and adding it back - I get notifications of this just fine, but the device is unresponsive it says and it doesn't work at all.
Its got to be Amazon --> HE cloud issues hasn't it?
Obviously I can't see the Hubitat cloud or Alexa cloud to look at logs though...