It there is a relay next to the engine ECU. It may have failed on you or gotten stuck. Do you hear a faint clicking sound from where the ECU is located on the rear left side of the engine compartment when turning the key to start position?
I thought that I had an immobiliser issue, but it turned out that it was the relay. You will not hear the faint click if it is the immobilizer.
Regards,
Jess