Immobiliser not turning off

[CMJToyota]

My year 2000 Corolla had a new alternator and Battery fitted last year and since then the immobiliser has become very tempremental. When I get in the car and try and start it the red flight keeps flashing and the starter will not engage. I found though that turning the key in the lock five times and then trying to start it works but this is obviously not a long term solution.

Any ideas on how to cure this please?

[Devon Aygo]

How are you unlocking the car:

Key in door

Button on remote fob

[Cyker]

When you hold the key up to the ignition barrel, does the immobiliser light change?

 

[CMJToyota]

Opening the door with the key.. The immobiliser keeps flashing when the key is in the lock. The key has a brand new Battery in it.

[Cyker]

The key doesn't need a Battery for the immobilizer - It just powers the door remote buttons; The immobilizer uses an induction-powered RFID chip in the key.

I have a feeling either the RFID chip has been dislodged or damaged and isn't being detected properly, or (Less likely but still possible) there is a fault with the inductor ring that surrounds the key barrel.

Things get a bit vague here, as I can't remember what style of Key the Corolla has - In some Toyota cars of that Era (e.g. my Mk1 Yaris) the RFID chip is built into the door remote transponder block, and there's not a great deal you can do with it. On other cars, the immobilizer RFID is a tiny black chip about the size of a grain of rice that's embedded in the key itself near the keyblade. It should be stuck in but if it's dislodged I seem to recall that caused problem with detection because they were very short-ranged.

 

[CMJToyota]

The keys look like those in the attached image. I have two identical black master keys as shown as 1 in the image. I was not given a sub key(2). One of the keys has lost the button covers 

[CMJToyota]

Bumping this topic as I am still having trouble with this.