yes, made sure of that. when we replaced the computer, immobilizer and key we used the complete ignition switch from the donor car
Do you have a second/different key of the pair to try.
"I called the mechanic. As soon as I mentioned the immobilizer, he said "I never thought of that, but, yes, the immobilizer could be the reason." I asked for his suggestion to resolve. He then described what would be the solution: Find all of your keys (I have three), then test each one. I might be necessary to lock/unlock the door using the door lock (not the remote lock of the key Miata fob), to as input into the system. For good measure, I unlocked the car using one of my other keys, then, as soon as I cranked the motor using the same key as I used to unlock the door, it sprang to life! I drove the car today with no problems.
As it turns out, the key I had been using exclusively over the past few days was faulty. The IC embedding into the molded plastic key head had failed. Evidently, it was borderline functional, until it finally failed. Each of the times the Miata could not sense the IC, it considered the key to be illegitimate, thereby triggering the anti-theft characteristics of the immobilizer. My other two keys, work great! This has been a real head-scratcher. Of course, all problems make perfect sense, once the root cause has been identified."