I do realize that there are more threads about this issue, but usually there's no follow up from support in them, although people still report this problem. So I'm starting a new one.
I have no working Google Assistant whatsoever. When activating it on my Venu 3, the Google Assistant opens on my phone and listens to my voice on the phone. But the Venu 3 just says "connecting to voice assistant" and after a while fails. Not just sometimes, every time.
I've already removed the Venu 3 from Android paired devices and Garmin Connect and set everything up as new. No change.
If you advertise a product with a feature, it should work, Garmin. Get to it!