Garmin Vivoactive HR wont power on HELP

My vivoactive HR appears to have died. The battery was low and I went to charge it. When I hooked it up the screen came on then faded and looked as if it had a dead battery(little battery with a lightning bolt) and then went black. It has been plugged in charging but there is not response. After a day or so I can plug it in and get the same response. I have tried resetting it but to no avail. Could this be a bad battery, or more serious problem….software?