Siri is not responding on Apple Watch after an update

On my iWatch, Siri is no longer responding to requests. Used to work OK but doesn't now and I'm not sure what changed, other than maybe the last update. Any advice from anyone on how to fix this? I've shut down and restarted my iWatch and I'm connected to WiFi, although I don't have to be.

I used to lift my wrist, call Siri, and then dictate iMessages which would be sent - doesn't seem to work now. Siri isn't actively listening so I press the Crown and the icon appears, but still no response.