As I don't have a X6 some "old fashioned" Symbian user suggestions , in following order :
1) do you have the earphones inserted ? The cable is the antenna .
2) have no other application running . Longpress Menu to check . And try again .
3) try a Soft Reset , bringing the device back to Factory Settings : dial *#7780# from the Homescreen . Also possible from the Settings Menu .
4) last , and some more work to do : Hard Reset . Make a backup first to save your personal data like contacts , calendar , notes etc .
Dial *#7370# from the Homescreen . First test the radio . When it is working , restore the Backup , but don't restore "Settings" . Do Settings manually all over again . When your personal securitycode doesn't work , Nokia default code : 12345
Hope you will get things together .