This issue is not resolved. Today I've discovered all my Hue sensors no longer trigger my Alexa routines. This can't be connected to the Alexa phone app. Routines that were working a few days ago no longer work. I've tried recreating them, removing the Hue skill and re-adding it, rediscovering devices. Nothing appears to fix it.
My sensors are configured through the Hue bridge, not connected direct to a Alexa Smart hub.
The sensors all detect when monitored in the Alexa App and the routines will run manually when you hit play routine.