Binatone f350 navigation problem?

hi i just bought f350 binatone nav satellite and it is not working properly when i switch it on it shows 2 options Navigation and Menu it does go to Menu but it does not go to Navigation option anymore i have been trying so hard but it just done respond anything when i touch on navigation option ? can anyone please tell me how to sort this out .do i have to install software again or what and how can i do that thanks i have also lost receipt so cannot change it either would be glad if someone could assist me thanks|||it might be the protective screen cover it might have bubbles in it.