Why is my HTC ONE M9 showing an hazard sign?

[Jack Odanga]

Problem started with my phone not charging after which I tried a few different charges thinking the problem could be the chargers. At some point it stopped charging and went off after power had drained. Later on, I try to charge it and it all works well but only charging when it is switched off. Today, I switch it off to charge but it charges up to 51% and stops and indicated an hazard sign, a red circle with an '!' at the center of the circle. What could be the problem guys?