lcd 20x4 configuration with xbee s2c


I am trying to configure the lcd 20x4 with the xbee s2c(part no.XB24CZ7UISB003-revL) but the display does not come on. The Lcd 16x2 is working fine but not 20x4.there is no display on the screen. Any idea what might be the problem. I am using the sample program an also changing the LCD 16x2 option to 20x4 on the config module page. The connection are verified to be correct as the 16x2 seems to be working fine.
(I thought I might have burned the chip so bought new one but the problem persist)