2002 Ford Focus ford rds radio not working

I HAVE A RDS FORD RADIO IN MY CAR , WHICH ONLY WORKS ON MEDIUM WAVE STATIONS AND PLAYS CDS , BUT ICANNOT GET ANY FM STATIONS , ITS IS RUNNING THROUGH THEM ,AND IT IS SAYING , NOT FOUND ON THE DISPLAY , IT HAS THE NAMES OF PROGRAMMES , LIKE ROCK ,NEWS , CLASSICAL ETC , WHAT HAPPEN IN THE BEGINNING WAS IWAS LISTENING TO A FM STATION WHILST DRIVING , THE SIGNAL ON THE STATION WENT OFF ,I TRIED OTHER ONES BUT NOTHING , I BOUGHT A NEW ARIEL ANTENNA ,, AND A BASE WHICH GOES INSIDE INTERIOR LIGHT COMPARTMENT AND TO FASTEN ON TO THE ARIEL WIRE CONNECTION . AS I THOUGHT THAT THE ARIEL ANTENNA BASE WAS WORN AS IT WAS CORRODED , AND PERHAPS WATER DAMAGE MAY HAVE GOT INTO THE ARIEL LEAD WIRE ,ALTHOUGH IT LOOKS IN VERY GOOD CONDITION , I WONDER IF THIS MAY HAVE CAUSED A DRY JOINT SOMEWHERE ? ANY IDEAS ANYONE THANKS ROBBIE