A1466 MacBook Air 2015 does not power on

Have a Macbook Air here that will not power on anymore. The light on the magsafe connecter comes on when it is plugged in and turns orange but nothing happens when the power switch is pressed.

From what i’m told it first just started to not power on then a few weeks later it would suddenly power on when tried then the owner was afraid to switch it off and left it powered on and it went to sleep after which it never powered on again.

I’ve opened it and disconnected the battery and it still does not power on when the magsafe is plugged in .

I’ve a good few years experience repairing PCBs but the only equipment i have at home is a multimeter. Can anyone point me in the direction of test points or a guide to troubleshooting this? I’m fairly competent with electronics repairs so please go into detail if possible.

Thanks in advance anyone! Any help will be greatly appreciated!