Silly question probably, but are your entities exposed to Alexa by default? I have all my domains set to “not exposed”, so all new devices have to be added manually.
Amazon is most likely having an issue with one of the devices that it’s discovering and bailing. This happened years ago with the media_player domain. Certain media_players would cause amazon’s discovery process to crap out. I recommend limiting the devices you expose to alexa and figure out which one is causing the issue. Then once you do, write up an issue mentioning what integration is creating the entity and also mention alexa.