green sensors not working

i’ve only had my apple watch series 1 for ab 2 years, and the past year my apple watch has been off and on with reading my heart rate. the whole reason i got it to begin with is because i have some heat problems. recently it has not been working at all. no green lights or anything! i’ve tried force reseting and un pairing and re pairing it both nothing works. i’ve looked in settings and made sure everything was on that needs to be on and eveything is off that needs to be off. at this point it’s just annoying. so plz if you have any ideas let me know!!!!