probably you have used the wrong QCOM number for GPIO23:
root@swi-mdm9x28-wp:~# echo 23 > /sys/class/gpio/export
[ 234.646922] gpio_map_name_to_num: find GPIO 10
I have also tried this PWM kernel driver to control GPIO23 in WP76 FW16.3, I can see the GPIO23 going up and down periodically: