Usually the immobiliser is deactivated when you turn your key to the on position when in the ignition barrel, then after around 3 seconds your red immobiliser light goes out (near your handbrake lever), you can then start the car successfully.
I'm not sure, but your central locking receiver may be different to your immobiliser function, both activated by your key fob.
I had a starting fault, after spending pounds on a diagnostic & new
sensor, found my intermittent fault was corrected by leaving the key in the on position, waiting for the red immobiliser light to go out & then starting my car. I found this out by reading my owners handbook, wish I did that first before taking my car to a Reno specialist.
If your car has not recognised the ignition key code, tell tale light will flash continuously.