Question My Pc isn’t working and I don’t know why.

[LocalFin]

I just built a custom pc And whenever I turn it on it doesn’t work. The motherboard light turns on but then shuts off after two seconds. I have replaced my psu three times and it still doesn’t work. So I reinstalled my ram and gpu still doesn’t work. I have been troubleshooting for a minute and don’t know what’s wrong. I built it last night and woke up tried to turn it on and it doesn’t work.

My specs are:
CPU: Ryzen 5 5600x
RAM: 2x8 Tforce ram
SSD: Crucial p3+
GPU: AMD 6600 challenger
PSU: gamemax 750w atx 3.0
Cooler: Stock cooler
Case: gamdias aura gaming rgb midtower white

 

[COLGeek]

What make/model motherboard?

 

[Ralston18]

If the PC is immediately turning off then I would suspect a CPU thermal shutdown.

What thermal paste was used and how was the thermal paste applied?