Why are my headphones not connect or turn on even after I charge them

Why are my headphones not connect or turn on even after I charge them
so i just recently got these headphones and they worked fine for a while, until the audio started to crack up and my main problem which is whenever i turn them on they just switch off, and the start up sound is very faint. sometimes they work but other times they do this, i really have no idea, i leave them on charge for ages and the charger light is on so i really have no clue.

ANSWERS: