Cardio fitness stopped recording

My watch/health app have stopped recording Cardio Fitness for both walking and running. Both the iphone and watch have the latest software. I have reset my watch. I have unpaired and paired my watch as mentioned in a previous post. It was fine until a couple of weeks ago (26th September was the last recording) and since then, nothing. I run 4 times a week and walks at least twice. I don’t know what else to try. I have an Apple Watch series 5 and iphone XsMax