bios – PC doesn’t boot with having 4-pin connector connected

Let me say the complete story
I have an old ADVANTECH PPC-174T aio device, some day I went to install Ubuntu on it, after that the display was totally wrong I googled and found out that turning off the internal graphics would solve it but I didn’t know it hasn’t any graphics but internal one.
So it wrecked.
After that I bought it to some PC fix servicers to fix it but none of them could fix it.
Now I understood the problem I have is No POST
found this link at the step 2 whenever I connect the 4 pin connector that’s next to CPU then the system doesn’t come up (I mean without connecting that Fans work, but with having it connected none of fans start)
What to do?