What were the conditions when you tried to make the shift and what range were you trying to obtain? After you turn the dial, if a certain conditions aren't met, the computer won't allow the shift to take place. For example, if the transmission (auto is all I know) isn't in neutral and you try to shift into 4 Low, the green 2 High will remain lit and the 4 Low light will blink- indicating that the proper shift conditions weren't met prior to turning the dial to 4 Low. If you were to return the dial to 2 High, place the transmission in neutral, then make the shift to 4 Low, the shift should then take place.
Ryan
P. S. - I'm assuming you have the electronic shifter. If you have a manual, then the gears may not have been lined up right within the transfer case, which may have prevented the shift forks from moving properly. By cycling the transmission from drive to park and back to drive, the gears may been "shuck up" enough to get them to align properly .