Only SMS and Call notifications are designed to be replied from the watch by one of the predefined answers. You cannot answer any other type of notifications.
You can request a new feature through the form https://www.garmin.com/forms/ideas/
I was able until a few months ago. Then my VivoActive3 stopped offering me the choices. Only have Ignore and Block now
I then got a Venu (same as a VA4) this Christmas and it also behaves the same way :(
Gotta be something with my Microsoft account or phone. Anybody has an idea. It was really useful not having to take out th phone for MFA.