2010 MAC pro won't bootup

The "approved method" for dealing with this situation is to remove everything that is in a slot:

all PCIe cards including the graphics card

all drives

all DVD readers (can just be cable-disconnected)

any external devices

You are going for the Chime, or a blinking power-on light.

If you get that, then you add back one item at a time and restart after each until something stops your progress.

If no chime, remove the RAM DIMMs as well and try again.

what does it do, exactly, when you push the power button?

Do the fans come on at a controlled level or not at all, or full force?

What does the power-on indicator light do? on solid? blinking a small integer "code" ?

On the display, does any background appear, or is it in a dark "uninitialized" state?