can't read push button value in dsPIC33
RE8 and RE9 are dual analog/digital, and by default ANSEL bits are set to function as analog, so you need to set ANSELE to 0x0000.
 Per the datasheet - 


  When the PORT register is read, all pins configured as
  analog input channels are read as cleared (a low level).


Also, the buttons are connected from pin to ground with a pull-up so they'll be low when pushed.