Using GPIO Pins with shared functionality

I am developing on an nRF52811 and I've noticed that I can't set/clear the pins such as the ones in the bracket in the picture below. 

I'm using nrf_gpio_cfg_output(pin_num) to see the pin as an output and then using nrf_gpio_cfg_set/nrf_gpio_cfg_clear to change the value of the pin, but I'm not seeing any changes. 

I've also tried this: nrf_gpio_cfg(0, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_CONNECT, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_H0H1, NRF_GPIO_PIN_NOSENSE); for configuration. I've also tried other pulls and drives just to make sure I'm not using the incorrect one. 

I am able to successfully change the value of the other pins (such as P0.06) with no problem. I'm not sure if I am missing a configuration step or if they're not able to be used in the way I want at all.