Can't boot, only apple logo then turns off.

Hi all,

I have an iPhone 5s 16GB which boots only to the Apple Logo for 10 seconds, then black screens for about 30 seconds and turns off. While in black screen mode, the backlight is still showing.

Prior to the incident, the screen was replaced along with the front cam and sensors, it was working for like few hours, then all of a sudden it turned off and the incident happened.

Trouble shooting:

Tried replacing the battery (original) = no luck,

Putting an original iphone 5s screen with original front cam and sensor = no luck

(with the original touch ID)

looked under a microscope, there seems to be no physicals of circuit board damage.

don't want to remove the shields until I am sure what the issue is.

I appreciate any help and tips.

Thanks.