My version of the Boeing 737-800 by PMDG's HUD is not displaying. I CAN deploy the HUD to in front of me, however the HUD will not "turn on". It just stays there, not lighting up with green text. I have had it before, and for the last week or so, it just hasn't shown up. I read the manual briefly and didnt see anything about it. I'm pretty sure that I pressed a button, just dont know which or where. Again, the HUD comes down, just doesnt activate text