MacBook Air not turning on

My MacBook Air (bought in 2016) turned off while I was using it and then said it was “installing Macintosh HD” for 36mins and then it turned off and I haven’t been able to restart it. I have tried holding down power key and also tried shift+control+Option+power, nothing has worked. There is no backlight to the screen and there is no change when plugged in to a monitor. It has the orange light on while on charge and doesn’t seem to change green light/fully charge. Any help greatly appreciated!