watch stops recording workout

I just played 90 minutes of tennis. The watched paused the workout at 16 minutes. This happens often. I bought a new watch band and it is snug on my wrist. I have Afib, and other health concerns. I record my workout to show my Doctor. I have also cleaned the watch (once a week) and it still pauses workouts. I am not happy it is pausing. I need this to work. I cannot find the wrist detection in the watch app on my phone. It was recently updated and apple must have moved it or removed it. anyone have any ideas? Its frustrating when you sweat for and hour. or more and the watch doesn't record the workout.