your not getting resonance because your cell has too much current leakage.
I would hazard a guess that your using tap water? Or water with too many impurities. The impurities act like electrolyte lowering your cells resistance. This is all the current in your cell traveling through like it is a resistor rather than a capacitor.
In SM's notes there is mention of different types of water and their amp draw. If possible increase your amp loading on your primary. How much to increase it by is hard to tell but once you hit the point where the amps can't pass through your waters resistance it will bounce back (increasing voltage) and try on the next cycle.
Remember your equation for resistance is "R=V/A"
As i see it, your cell will resonate, increasing in voltage, until it has built up enough volts to allow the applied amps to transfer through the resistance (water). So if your cell will allow your applied amps (note that your applied amps is the OUTPUT from your VIC) to transfer through your cell at 120V then that is your voltage point.
To fix this (as per the above reasoning) you will need to INCREASE your cells resistance, or INCREASE your amp output from your transformer. Just a bit of IMO
