Question PC doesn't turn on. Help me find the cause.

[IDProG]

The situation:
1. The PC does not turn on
2. The external HDD lights up after I plug in to the front panel USB port, meaning that power gets delivered to the motherboard to the point that it can power the HDD.
3. The fans do not turn on

Let me know if you need more information on this. I'll add more context as I re-test the PC.

 

[Lutfij]

Did you breadboard the parts to see that they at least work out of the box before dropping them into you rchassis?

When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:

We can move forward from there.

 

[IDProG]

When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:

We can move forward from there.

Most of these do not matter, at least not yet, but I understand what you mean. Thank you for the comment.

The case is NR200. The PSU is Seasonic Focus Gold. I haven't checked if the PSU fan turns on.

Like I said, I'll add more context as I test more of the PC. But for now, what I said before is what I have.

 

[IDProG]

UPDATE:
The PC CAN turn on. The cause of it not turning on last time is that the front panel connectors didn't get plugged in right.

But, now that the PC turns on, I can confirm that I can't get to the POST screen.

Here are my specs, now that they matter a lot more:
CPU: Ryzen 7600X (so no iGPU)
Motherboard: ASRock B650E PG ITX
GPU: MSI GTX 1070 Armor (old GPU)
RAM: 2*16GB DDR5 G.skill Flare X5

I touched the heatsink of the CPU cooler (Thermalright Peerless Assassin), and it was not cool, meaning that the CPU produces heat (I don't know if it is an indicator that the CPU is not faulty).

I plugged in the DisplayPort cable to the GPU and the monitor, and it shows "no signal", meaning that the GPU fails to bring what's being processed to the monitor. That, or there's nothing to display. The GPU fans do spin, and I can confirm that the monitor is NOT faulty.

Since the PC turns on, the PSU is not the problem.
I don't think that I require an SSD to go to the POST screen. So, that one comes off, too.
So, the potential problems are the CPU, GPU, and RAM, maybe the motherboard on the CPU or the PCIe slot side.

EDIT: Oh, the 7600X DOES have an iGPU. I just read that!
I can't wait to test it. If it POSTs, then the GPU is faulty. If it doesn't, then the CPU is (or the motherboard).