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.

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" ?

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

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