If you are being literal your missing -p before your c=GBX I think
you don't need a password (-p) if there is no password
The pool takes the arguments you pass with -p, and makes decisions on them. If you just set "c=GBX" you are setting that on the miner, which is probably ignoring it. You set -p c=GBX (or whatever) and the entire argument gets sent to the pool, which then dictates your payout coins.