New battery no charging no power

This phone is several years old and has worked flawlessly so I thought worth fixing. It recently started getting very hot when powered up and not holding a charge. Just installed a new battery carefully following your iFixit guide. Not a simple procedure but I double checked, all physical connections were good. Power button was in place on reassembly and volume sensors in place as well. Now when plugged into 5v 2.1amp charger (or any other for that matter), the red light flashes once every second but the phone never gets charged and will not start. I have held the power button and volume for over two minutes, plugged and unplugged. I then get a solid red light for one second, then a short green light for 1/4 second, then a red light for one second, a one second pause, then five red flashes at one second intervals. Then the sequence starts again. It never charges up and will not power up. Is this thing toast?