S62 Heart Rate Monitor Issues

Hi - I have a new S62, and today I connected it to my Peloton bike to use as a heart rate monitor during my ride.  I noticed immediately it wasn't registering my heart rate correctly - the highest it read during my ride was 107 (i am not in that good of shape).  I should have been at least in the 140 range. Has anyone had trouble - or do I have something defective?