Power on from motherboard

Hello,

I have a Galaxy A3 2016 ( 310F) with a broken LCD. The phone is pretty much destroyed everywhere so I have not intention of re-assembling. I have connected the new display and when I connect the USB cable the display lights up with the battery % charge. When I press the home button the same screen pops up.

However I seem to be having issues actually booting the phone.

I tried it like this guide:

https://youtu.be/yIp51gcTcpQ?t=882

But that doesn't seem to do anything.

Are there any other ways of booting the phone from the motherboard, or am I doing something wrong?

Or do I have to take out the b atteryu and pop it back in?