Well, if there's no plasma, it's logical that no current is flowing. Here is a (potentially incomplete) list of possible reasons:

• external hardware: the power supply and also the external cables may suffer damage. Especially if one end of the cable is attached to moving parts of the sputter module, the plugs may wear out and cause contact deterioration. This may be true both for the main as well as the control voltages.
• contamination of the target: if it has been poisoned by a dielectric layer, at some point a regular, non-pulsed DC voltage may no longer be able to get through.
• jamming of gas inlets: if the gas distribution is faulty, the plasma may flicker or even not ignite at all.
• coating of the chamber shields: the plasma may require a certain resistivity and if you have dielectric coatings on relevant parts that should be conducting, this may fail.

You are unable to strike the plasma.

- Check your sputtering pressure.

- Use a simple metal target like to Copper for testing purposes

- Your HT electrodes may be shorting with the ground inside the chamber, clean up the areas around the contact, and cover with teflon shields.

Try to strike the plasma, and vary the pressure for max current.

K. Sreenivas Checking for shorts between parts is indeed very important, I forgot about that.

Significantly increasing the Ar gas pressure can frequently help to ignite the plasma (i.e., raising to ~15mT, then back to our normal ~6-7mT once ignited almost always works in our system)