Why is my pull-up resistor not working?
When switching high-side power using a p-channel FET, I always drive a small N-channel FET to attach to the pull-up,  I'm not experienced with your particular processor, but Microchip processors don't do a good job of driving the outputs up to the positive rail especially if the signal has other stuff on the line.  They do however go low enough to turn off the N-channel FET which will insure that your gate goes all the way to the positive rail.  Note that this will invert your logic..  It also has the advantage of allowing switching of different voltages and is turned off when the processor output is low during startup.