Power Light Flashes On then Off. No Boot Process

I have about 20 C720s that have the same issue. I try and turn them on and the power light flashes and then nothing. I have tried the following:

- Refresh and power - does the same thing as just hitting the power button

- Esc Power Refresh - does the same thing as just hitting power

- I suatered the super secret button and before you say that’s probably the issue. It was happening before the sautering and I have sautered others and not had this issue SO THIS IS NOT THE PROBLEM

- Unplugged all hardware except keyboard removed power adapter and battery then held power button for two minutes. I then started reconnecting hardware to trouble shoot which piece may be the issue but again, it continues to fail to boot. However, with about a third of them once I put all the hardware back on they started up under the recovery mode, but then would freeze when recovery media was inserted or wouldn’t boot after recovery media was installed.

Is this the MOBO or am I missing something?

Thanks for any advice.