More info please...
Has it worked for you before or has it always been a problem?
What are you seeing? Do you get the menu and just no pitch change or is the effect greyed out before you start?
Are you doing it in the Waveform/Edit view or trying to put it in the effects rack in Multitrack?
...that sort of thing.
And, very importantly, which version of Audition on a Mac or a PC? And which operating system?
And exactly which 'change pitch' effect are you referring to - Automatic Pitch Correction , Manual Pitch Correction, Pitch Bender, Pitch Shifter or Stretch & Pitch