PS4 Pro beeps and turns off

Hi I have a PS4 Pro i took it apart as iv done before to lean it this time after i put it back together it beeps once shows the blulight and goes off.

iv taken it apart and i take out the psu and just leave the 5v cable connected to the board i get the exact same issue.
if i plug the psu in to the board and put a tester on the back of the long flat 12v connectors i can see that the psu gives 12v to the board for a second and turns off. I think this is normal and i think it sends 12v to the board and the board is ment to reply then the psu starts pushing 12v and its should start up.

but this one is not doing that, so it looks like the board is not getting back to the psu and the psu thinks there is a problem so it turns off.

how do i fix this?

Did you make sure to put the clamp on correctly?

you mean the apu clamp?
i think i put the cover over on the the bracket pushes against. Then finger screw in each of the bracket screws a few turns to catch the thread, then screw the down a little at a time working in opposits like tightening up a wheel. north, south, east, west or 1324. I do the same with the CPU’s heat sinks i work on.

Yeah, but if you put it on properly that’s most likely not the issue. Maybe when the console was opened something got hit off the board or a trace was scratched? I would check for anything obvious first, and if there is nothing like that you might have to start testing components.

sounds like a southbridge issue