Repair Help - MacBook Pro 2014 won't turn on, charges and SMC reset works

[Monkeys]

Hi all, just looking for some advice on trying to repair a MacBook Pro 2014 which won't turn on but will charge (power cable turns to orange when plugged in). SMC reset (command + option + shift + Power) seems to work as it causes the light on the power cable to turn from orange back to green for about 2 seconds, then back to orange again.

Device has no liquid or drop damage, it just stopped working one day..

Any ideas on what is most likely the issue?

 

[Audit13]

Remove the bottom cover, disconnect the battery for a few hours, connect charger, and see if it boots.