Motherboard problem? PC doesnt boot

[Ivan Salas]

my motherboard is an asus ROG STRIX Z270E and i have it since last year, i recently change of PSU, upgrading from 600w to 750w, since i change my PSU my PC does not boot the first time (it turns off by itself), but if i try again it does, i noticed that after the ROG logo loads the PC shuts down, the second time works fine, full load for hours, i can keep the PC power for days, no problem there, but if i shut it down the PC shuts down after the ROG logo loads, if i reboot there is no problem, only when is turn off, i got a PSU from a friend 650w, brand new, he told me to use it for test if the problem really was my PSU, same problem, the same thing happens. i tried using both PSU in different combinations, nothing works, so i concluded that the problem has to be the motherboard, i hope someone could help me find out how this happen and if i can fix it, i already updated the BIOS 2 times, didnt help

 

more info:

2 SSD

1 hard drive

1 M.2

GTX 1080 EVGA FTW2

i7 7700 (non k)

16GB RAM DDR4

PSU1: corsair tx750m

PSU2: evga 650