CAN'T START - No connection to Ktuner ECU and immobiliser light on.

[monty]

Hi,

My DC5 Type S (Australia) has sat in a workshop for almost a year without a battery. It was undergoing some engine work.
All works are now completed and car is ready to start but unable to get the fuel pump to prime and spark when cranking. Initially thought it was to do with fuel pump wiring but have double checked everything and confirmed that ECU is not sending a signal to the fuel pump.
Popped open ECU cover and can see the Ktuner board's LED do not light at all when keyed on. Suspected faulty ECU but tested the ECU in another DC5 and the board LED light up and connects to a laptop fine.
I've also tested for power and ground on ECU connector A:

• A2,A3 power when key on
  A4,A5, A23, A24 grounded.

Also noticed the green key light is flashing on my dash and no key chime when key is left in ignition. Nothing has been touched on the wiring side when works were being done (apart from unplugging the harness at the engine side to drop the engine). Have gone through every single connection on engine side to check that everything is plugged in fine and also checked over every single fuse and relay at the ECM,PCM and fusebox.

Immobiliser is factory, not aftermarket. Can the immobiliser be 'reset' if the car is not connected to a battery for extended period?
I've tried reflashing the ECU by connecting to it in another DC5 and disabling the immobiliser with Ktuner too. Is this enough to entirely bypass the immobiliser hence ruling out an immobiliser issue? I'm still leaning towards an immobiliser related issue due to the flashing green light.

Otherwise I'm completely stumped and next course of action would be to try and test every single pinout on the harness??

Any help is appreciated, just need some direction on where to look next.

[KTuner]

The Immobilizer doesn't prevent ECU power, so that's not your issue.