Does the Sigma 500 DG Work with a 1D Mk II?

Guys,

I'm just trying out the Sigma flash with the 1D Mk II and can't get it to fire.

Facts:

1) Pressing the "Test" button fires the flash
2) The flash is showing ETTL
3) The flash emits the AF assist beam
4) The flash "zooms" with changing focal length on the lens.

It seems to do everything except flash when I pull the trigger (and yes, I'm testing this in my garage where it's nice and dark).

Ideas? What am I being a dumb-ass and forgetting?

It should work.

Maybe try removing the flash unit, cleaning the contacts and try again.

Thanks Curtis.

I worked it out - the batteries didn't have enough charge. I put them on charge for an hour and it now fires correctly. I guess I was diverted by the fact that everything else seemed to work fine.