Asus Z270A not booting, no beep, no fans

b.purer

Prominent
Feb 4, 2018
3
0
510
Asus Z270A
Intel Celeron G3930
DDR4 2400 8GB
Corsair RM650x
no vga (only onboard)
no ssd

Hi folks, hope you can help.

I already done everything I could find in the forum. I switched everything off like VGA, SSD, USB Connectors etc. The only things which are plugged in are:
CPU
CPU FAN
MOTHERBOARD 24 pin power and 8pin cpu power
Reset and power button
DDR4 RAM in DIMM A2
Chassis fan which is connected with PSU and not the mobo
Mouse, keyboard, monitor

When I switch on the PSU the green power LED on the mobo goes on. When I press the power button nothing happens. No fans, no beep.

Someone’s got an idea?