Questionmark folder when booting from SSD

Hello,

I have a Macbook Pro 13 Retina Late 2013 (A1502) that won’t boot, I get a questionmark folder upon start.

The SSD has been switched to a new one and still the same problem.

I have a logic board (820-3536A) which I am currently investigating. I have the schematics to the logic board and the ssd socket gets about 3,3V from L3700, meaning that the ssd socket gets power which I checked first.

I saw on youtube that Louis Rossmann also checks the reset to the ssd at component U3740 pin 3 and 4, he gets about 3,3V there and I get close to 0 V. I think there is my problem but does anyone have experience with this kinda issue? I’d love some help and I will answer any further questions to solve my problem.