raspberry pi 3b+ wont boot

Question

Hi there!

I have 2 raspberry`s.
One is working fine and well and if i want to turn on my other raspberry (with the same SD card what i used for the other) the ACT led is just blinking 4 times and wont boot the raspberry.
I checked and 3v3 and 5v is there. I tried 2 types of Adapters 5v 1A and other other is 5v 2A and with both Adapter was working fine (just 1 raspberry) and the other raspberry was still not working :(

My question is what could be the problem that it wont boot?

Answer 1

This site has a list with errors:

https://elinux.org/R-Pi_Troubleshooting

Answer 2

Defect.