Please forgive me if i am asking a silly question.

I installed the 1.4.7 in my 770 (latest firmware)and downloaded the repositories also. I didn't have any issue till this point. I don't have GPS and i believe that i can download standalone maps. hence i gave an origin and end point and clicked download button. it said route downloaded. but the screen is blank completely black. Whats the reason for this? i even made full screen and it didnt work. i also removed the option of "Enable only in full screen mode" nothing worked. help me