I recently bought a JK BMS as well, but I remember the GPS port being for something else, and not actually GPS.
Now its going to bug me, I have to figure it out.
Also, for OP, my new one did not require 5v be applied, the new ones only require you to short 2x pins for longer than 1 second and it will turn on. For me, it was the farthest 2 to the left.