help with corsa c not starting?

I have got this corsa c on x reg. The f flashing on dash. And it won't go off f. Its got a tricktronik hear system.

I have changed gear box sensor. And water pump.

I have tryd putting throttle and brake down but f just keeps flashing.

Any help ?

Its was running fine yesterday. I parked up then in morning car givin me nothing. I get all lights working.