Heart Rate on Apple Watch isn’t calibrating at all

So my Apple Watch has been working perfectly fine but today when I woke up I went to go do my basketball routine and pressed the workout button, after I did my session, it showed 0 calories burnt and 15 minutes in, I realized that the heart beat wasn’t working and I tried everything, general->privacy and checked if everything is on which it is, my heart beat hasn’t been calibrated since yesterday and idk what’s wrong with my watch so can someone tell how to fix it.