Got my 645M 4 days ago. It was working fine up until yesterday, then the HRM functionality stopped working. I observe that the green led never comes on anymore, and the watch never detects a heart rate (except in broadcast mode, where it shows a number no matter what, even if it isn't on my wrist).
Things I've tried
1) Disabling and re-enabling wrist HRM via both the watch and garmin connect from the phone
2) Rebooting the watch
3) Resetting the watch back to defaults
Is there anything else I can try?
Thanks,
-Andy