Over the christmas period my tf suffered a flat battery i recharged it overnight disconnected from the car, The following day i reconnected the battery on trying to start the car all that happens is the engine runs for thirty seconds then stops, I have replaced the fob batteries but still no joy can anybody help.
Not sure if all MGF/TF have the same system, but my 160 TF needs to have the immobiliser resync`t if I disconnect the battery. Also You might need to resync the fob if you have removed those batteries as well. You should find the process explained in your manual.
However if you have managed to lock and unlock your car the fob resync looks to be not neccesary.