Different cpu works on the motherboard and the cpu that came with the motherboard works with another

So I stumbled upon an anomaly, my friend passed some spare parts from his G3620 predator and when I went to boot the machine, it would not give a signal, you could hear the post beep indicating that it was a normal startup so I tried Everything in the diagnostics book to attempt to get it to give a signal. The motherboard and cpu I was given were the I5-3350P and an ácer IPIMB-AR motherboard.
The motherboard and cpu work, I tested the CPU on Another motherboard, it worked, I tested the motherboard with Another cpu, it worked and booted up but when I try to get the two Components that I recieved to boot, it just won't budge. I've tried resetting the cmos, I've tried updating the bios, reverting to an old bios update while making sure all Components I tested worked but I can't seem to get it to give a signal with the motherboard and cpu that was inside of a G3620, that I previously tested before we dismantled the build.

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Sobe

When you say signal, what do you mean? Like to show up on the monitor?
I assume you are trying to get into the bios? Were you able to ?

Arek_

There's no signal on the monitor when I run the following setup
Acer IPIMB mobo with the 3350p - THESE ARE COMPATIBLE AND SHOULD WORK, THESE TWO COMPONENTS CAME OUT OF THE SAME COMPUTER
but it gives a signal when mixing up.
3350P inside an Asus p8h61-mx WORKING SIGNAL
Intel Celeron G550 inside the ACER IPMB-AR WORKING SIGNAL
3350P inside the Acer IPIMB-AR NO SIGNAL
I've tried multiple monitors, I've tried onboard graphics, I've tried graphics, all of the mentioned work when the 3350P is not paired with the IPIMB
It's an anomaly I don't think I've ever stumbled upon. I've been working with computers for about 5 years or so now. This truly is the first, I've worked on lots of machines in my time, done some diagnostic, troubleshooting and even repair. BUT THIS
As much as I hate to admit, I'm confused.

Sobe

Such an interesting situation. It seems like you did every possible troubleshooting steps that I would take.

I bet it could be an easy flick of a switch that we haven't come across yet.

Are you saying that when you put both Acer IPIMB mobo with the 3350p, there's no signal to the monitor, BUT can you still tinker into the bios? Or even tinker into f8 boot such as safe mode, etc?

I would troubleshoot in the areas of:

The ram stick (if there's two, use 1 and play with that and switch to different slot or try a different ram),
The motherboard's onboard video, bios setting for video (pcie or onboard), and external graphics card.
Have you tried a different PSU, and the CPU connectors that is securely in?
Check Jumpers?

Arek_

I checked everything. I triple checked everything.
I get a signal signal with both onboard graphics and dedicated graphics but only if if the combo isn't paired up together.
IPIMB works with a different cpu
3350P works with a different motherboard
Pair the two together, same psu, different psu, same cmos, cmos reset, different cmos battery and it won't work. It's as if they're not compatible with eachother when in fact they are since they came out of the same machine.