Make sure you are calling the function
Code:
Set_Number_of_Analog_Channels(SIXTEEN_ANALOG); /* DO NOT CHANGE! */
In User_Initialization(). Otherwise, I really don't know what to tell you. Make sure it's connected to the RC properly (wire ordering), there are no breaks in the PWM cable, that the wires are SECURELY (i.e. soldered) connected to the pot, and that you've tried it with all the analog inputs (well, 2-4 of them should probably suffice).
Good luck.