Apologies to @CHRISS

PBked

I was just browsing some recent posts including my own and realised the response I gave to @CHRISS seemed very flippant. What I meant to say was 'try putting a different lens on the camera'. Although it is true that F0.0 is displayed when no lens is attached, this can also be true when the lens is not communicating with the camera. The reasons can include dirty contacts on the lens or camera, wrong mounting of the lens (red dot to red and white dot to white), a lens not compatible with the Canon EF system, or a faulty lens or camera metering. If you mount a different lens and get an aperture reading, then this would indicate that the first lens is faulty in some way.
Once again, my sincere apologies.
PBed