I recently purchased the Gravity Heart Rate Monitor Sensor for Arduino from your website, but have been experiencing some issues with the sensor

Despite trying to position the sensor for an hour, I have not been able to get any usable results. I have tried positioning it all over my body, but it has been extremely finicky. I suspect that the problem may be with the sensor itself, but I wanted to see if anyone has any suggestions. I have checked for possible causes, such as ambient light, movement, and electronic noise, but the sensor is still not working correctly. I also tried loosening and tightening the band, using digital and analog modes and various example code snippets, but to no avail. The red LED indicator on the board itself also seems to be having the same problems as the sensor outputs, which leads me to believe that the sensor may be faulty. Any ideas?

Did Robotshop contact you for replacement? I think the sensor must be checked by them. Because you have tried pretty much everything to get it working. By the way, it is true that sometimes it is difficult to place these sensors tightly under our vain. I find this type of arrangement more convenient.