I used the 'A' button reset, the green lights flashed once, then stopped.
I tried it again, for a longer time, same thing, flashed once then stopped.
I turned off the HR and the Activity feature. Waited, turned them back on, then went to phone app, noticed a flashing of a screen telling me I connected to something, then disappeared before I could read it well. The HR monitoring started working after that. This is the second time it stopped after charging. I contacted Help, but it seems then will not be available for helping until Monday (phone calls,) another time (Chat,) Garmin doesn't answer emails. To date, the HR was the ONLY feature that functioned well. Without it, the watch is nothing more than a watch.
Has anyone learned why this happens?