Gravity Lightning Sensor SEN0290 Not Working Correctly

Hi

I have interfaced a gravity lightning SEN0290 sensor to an ESPC6-C6-Zero using the Arduino IDE and the example in the DFRobot web site. However, I can get no response from the lightning sensor (ie no response from IRQ pin) when attempting to trigger the device using a pizzo gas lighter and also a hand help VHF transceiver held close to the sensor. 

I have ascertained that I'm talking to the the SEN0290 correctly by writing and then reading back a noise floor setting, and the program appears to be running correctly.

Ie 

    noiseFloorG1 =  lightning0.getNoiseFloorLvl();
    Serial.print("Noise floor before is ");Serial.println(noiseFloorG1);

    noiseFloor = 5;
    lightning0.setNoiseFloorLvl(noiseFloor);
    Serial.print("Noise floor SET is ");Serial.println(noiseFloor);

    noiseFloorG2 =  lightning0.getNoiseFloorLvl();
    Serial.print("Noise floor after is ");Serial.println(noiseFloorG2);

this works as expected so I think the I2C is ok

Thinking that perhaps those sources above can't trigger the device, I tried commentating the lines intended for tuning and attached a CRO to the GND & IRQ pins as suggested.

Ie 

   lightning0.setLcoFdiv(0);
   lightning0.setIRQOutputSource(3);

This just shows zero volts on the IRQ pin.

Strangely, if I set 

   lightning0.setIRQOutputSource(1); 

I get a 35.86 kHz square wave on the IRQ pin, and if I try

   lightning0.setIRQOutputSource(2);

I get a 1.3 MHz square wave.

I conclude from this that the IRQ output is active, but only when I set if for TRCO or SRCO (whatever they are) and not for LCO

If anyone has an idea of what might be wrong, or what I should look at next, I'd appreciate hearing.

Thanks

Steve