Hi,
Try to use digitalPinToPinName instead of digitalPinToInterrupt when calling nrf_gpio_cfg_sense_input, which will expect a nrf_gpio pin input (should be P0.11). However, digitalPinToInterrupt will only return the Arduino pin number, they are not matched. digitalPinToPinName(P) will do the pin mapping, g_ADigitalPinMap[P] will also work, actually which is the definition of digitalPinToPinName.
nrf_gpio_cfg_sense_input(digitalPinToPinName(int1Pin), NRF_GPIO_PIN_PULLDOWN, NRF_GPIO_PIN_SENSE_HIGH);