I seem to be having same issue as described by others here
I have:
1x Gen 2 Dot with version 644580520
1x Gen 3 Dot with version 2785573252
1x Echo Plus Gen 2 with version 2785573252
1x Sonos Beam (integrated Alexa) with version 5200013
All was working with Alexa Hue Bridge plugin until about a week ago when Aexa Hue Bridge plugin suddenly stopped detecting devices.
Tried everything in this thread so far but no joy:
1. Turn off all devices apart from Gen 2 echo dot and rediscover - no luck
2. Remove all devices from alexa.amazon.com and rediscover - no luck
3. Restart plugin and rediscover - no luck
4. Create new Alexa hue bridge with single device setup and attempt rediscovery - no luck
5. Restart Indigo Server - no luck
6. Reset power on router - no luck
7. Ensured ethernet is OFF and only wifi connected on mac Mini HA Indigo Server - no luck
Guessing from above comments its the xxx520 s/w update that stopped it working.
Have i missed some other options to try and bring my setup back to life? I miss the convenience of Alexa throughout the house with Indigo controls.