hal8k

I use the same gpio library and all pins are working on my OPi Zero.
It may be worth re-soldering pin 9 on the IDC header and see if the soldered
connection is at fault.
 
Below is  a very  quick bash script to set all pins as outputs, activate them,
then turn off all pins you can use as a check.
There's probably more efficient ways of doing the same thing
 
#!/bin/bash gpio reset; sleep 1; for n in {0..30}; do gpio mode $n out; gpio write $n on; done gpio readall sleep 3 for n in {0..30}; do gpio write $n off; done gpio readall; sleep 3; gpio reset