"not tuning" might actually be "no plasma", if someone else is reporting the problem. That can usually be remedied by increasing the pressure until you get ignition. That was common on a manual sputtering system. It didn't happen to often, but it did.
There was a plasma view port. This was manual tune only. It also did DC sputtering.
On an automated PCVD system I helped put together, there was a Plasma Bias output on the ENI RF power supply. I interfaced that using an Analog Devices isolation amplifier, so we could determine ignition and get the correct deposition times. I THINK it mattered where you set the initial conditions too. I didn't do the recipies, but I did do all of the electrical, RF and electronics.