ADC on PIC24FJ64GB004 not working
I'm not sure what compiler you're using, but it seems that you're not calling the function that actually triggers the ADC conversion or setting up the ADC before you use it. Usually the process to use the ADC is:


Configure ADC
Open/Enable ADC 
Check to see if ADC is not busy
Call ADC convert function
Check to see if ADC is not busy
Read value in ADC registers 


These functions are usually defined in the compiler manual library. So you could check there to find out the exact functions you need.