Ring second gen won’t charge

My Ring will no longer charge. When plugging in via the USB port the light flashes for a few seconds (complete blue circle) followed by a minute or so of nothing. It then repeats this cycle. I do not see the percentage charge lights at all. I have left it in this state overnight and it never charges. I have tried several USB cables and power sources with no success. I suspect a battery failure but this model does not appear to have a user-replaceable battery. I have had the unit for two years so out of warranty. Any suggestions?