Solved mine yesterday, was a dirty charging port. I turned my phone off then using a alcohol pad and blunt end of a needle, careful wiped the contacts. The dirt removed was visible on the pads so im sure the cleaning worked, i left my phone off for a few minites afterwards to let the alcohol evaporate then powered my phone back up. The problem appears to be corrected. Yes there is some risk to poking a rigid object in that port so be careful but a dead phone is useless in either case. Good luck.