It will show light blue if you are not in "Flight Phase". You can put it into Simulation Mode and get some speed (greater than 35kts and Altitude, then Touch NRST and the Red Triangle. You should see them turn Red. As you fly over or near airports, those will turn Yellow and Green, depending on your glide ratio. Be sure to set the Glide Ratio in your aircraft profile.
If you are on the ground or not moving fast enough to trigger Flight Mode, there is no Glide Guidance. Hopefully this helps.