Power Pads on a 1398 Mid 2015

@rany you might want to stick with phones. The OP is looking for the two spots on the logic board that when shorted will cause the machine to boot. Obviously his machine is not booting when pressing the power button. This is most often caused by a liquid spill that has shorted out the keyboard.

@mayer how do you prompt a 2015 MacBook Pro to boot if you don't have a keyboard attached?

@mayer what's wrong with @rany's answer? It will boot when plugging the charger in (after the battery is reconnected), so if it boots this way (with the keyboard plugged in/unplugged, in case this is preventing boot) OP knows it is a keyboard issue.

This is by far the easiest way to check for a bad keyboard, I work on a lot of MacBooks daily and never have had a use for finding the power pads; no need when it boots up by itself when the charger is plugged in.

@rany FYI, the fans will spin straight away on the 2015 15" when booting, it is only the 2015 13" where the fan will spin once it needs to cool down :)

Thanks @reecee, I edited the answer to remove the part about delay in fan spin.

I think you are missing a step in the original answer. I think it should say that after disconnecting and reconnecting the battery, the machine will boot upon connecting it to power, without the need of pressing the power button. Is that correct?