Apple Watch Only Counting Minutes, Not Counting Calories

Hi there, I have a new iPhone and I connected my apple watch to it and now when I record a workout on my apple watch the active & total calories stay as 0. When I review my workouts on the fitness app, previously the workout would show as the number of calories burnt, but now it shows as minutes

I unconnected & reconnected my apple watch but it hasn't seemed to fix the problem