I think he means that this is a high-voltage circuit, the same as found in xenon strobes and camera flashes. The 350V rating on the cap definitely confirms that.
So, it might be the 350v capacitor has failed and is not storing enough charge to generate a meaningful flash, or the trigger circuit which is not generating the initial >5kV to get the xenon conducting.
Either way, i'd check the circuit before the xenon tube.