Computer automatically powers on but never actually powers on

I have an Acer Veriton M460, I recently replaced the motherboard on it. plugged everything in and then plugged the power in. It immediately started running. The fan for the processor and power supply started to spin but I never had to push the power button on the front. When I look at the button the light never lit up and when I would push the button it wouldnt do anything. When I held the power button in, it wouldnt shut down the computer. To shut it down I would have to pull the plug. Now whenever it would turn itself on automatically, I never heard any beeps or anything, the fans would just start running. So I disconnected everything that wasnt esential, USB's etc plugged it in, still the same thing, unplugged the power button same thing. I pulled that motherboard out and stuck the old one in, *which would work sometimes but not all the time I at least would get some beeps* and the exact same thing happened. Does anyone have any idea what is going on?

Make sure you have the 4-pin 12 volt power supply connector connected near the CPU socket on the motherboards. Also, make sure you are not shorting out the motherboards to the case

It is connected, and im pretty sure im not shorting out the motherboards. How would I be shorting them out to the case?

Well, you have to make sure that the motherboard standoffs are placed properly underneath only the mounting holes in the motherboard, and no extras are still under the board

In that case the answer would be yes it is properly placed.

Do you have the case front panel wires plugged into the motherboard header properly?

Well I only see one spot that they should fit into, and it says panel so im pretty sure its plugged in properly. On the other end when you pull the front panel off the cables are connected properly as well.

Do you think its possible that the power supply may have some issue, either the 4pin doesnt work or is shorting the board out in some way?

Yes, it's a good idea to try another power supply

Had some issues with a shipment, but eventually got both the power supply and the motherboard. It now works perfectly fine so I suspect that the power supply shorted the board. But its all fixed now.

Thanks for the update and happy computing