Problems using Siri with Fenix 8

devices: Fenix 8 AMOLED 47mm 13.35FW, iPhone 16 pro iOS 18.4

when I hit the phone assistant button, I get the microphone icon which appears to listen, I get a sort of sound that suggests Siri heard the command then the symbol vanishes with nothing happen.

I've tried asking it to make a call or ask the time. 

Siri works fine on my phone itself. (I have been putting my phone face down on the desk trying out this feature)

I can answer a phone call from my watch and the mic/speaker work fine.