infinity problem, please help

2001 infinity qx4 needs help. when attempting to turn the car on, it turns over like it wants to start and nothing. the red security light is on when ignition is on and was told that there is a problem with nats system. prior to the issue, i was able to get it started twice, but it shut off immediately after it fired. the machanic i took it to said that the issue has something to due with the immobilizer and that there is software that only manufactures and dealers have??????????what can i do to avoid paying 00000$$$$$any help and advise would be greatly appriciated.
ryan
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