If the red security light is still flashing when the engine is cranking NATS hasn't been deactivated and the vehicle will not start.

The main thing that goes wrong with NATS in the ZD30 is the IMMU (unit around the key barrel that reads the key).

It is also possible to have a faulty key. Do you have a second key? Have you tried starting the vehicle with it?

I have been told that some locksmith can check a key to make sure it is sending a signal. Not sure if this is correct as I haven't asked any or if they can check if the signal is correct.

There is a reset procedure in the owner hand book incase the key signal received interference from something. I don't thing this will work for you but it's still worth trying.