Mini Roof Rack Clamping Plates not moving

Hello, I recently bought a second hand roof rack; the rear bar seems fine, I can open and close the clamping plates by hand.
However, the front bar's clamping plates are not moving at all by hand. They won't budge and they stay in the open position.

OPEN position:

I would like to be able to move them into the closed position which will be necessary when mounting them on the car.

CLOSED position:

Finally, is there a proper way to loosen the clamping plates mechanism so that I can move them by hand without breaking anything?

Thanks

 

Those are spring loaded, and the spring is pretty stiff. Did you get the tool set, too?

This video is pretty good for showing the installation procedure:

 

I have the lever to press in the clamping plates and the dynamometer key.

I can install the rear bar with no issue since the clamping plates on that rear bar can be moved from open to closed position by hand.
However the front bar's clamping plates seem stuck.
I'm asking for a way to unstuck them.
If you know how to, please let me know.

 

The clamps mechanism was rusted enough to seize.

I drowned it in WD-40, let it sit for 15 minutes then I grabbed each plate with a 1 foot vice-grip and after a couple tries it finally became loose again.