Siri isn't working on my MPB

I can start Siri on my MBP 2016, and I get the beeps. But when I speak, it just doesn't react, and eventually it shows a message that Siri couldn't hear me, and there was a 'Siri audio problem'.

I can dictate perfectly well into Google's search bar, for example, so the microphone is working.

Internal microphone is set as the input for Siri.

Any thoughts how I can problem-solve this? It used to work...

Thanks