did you try placing the inductive loop in front of the ignition switch as you did with the key and if so did it work? if it does then it is definitely placement, other than that the wire coil is not working. you sometimes have to wrap it tightly around the lock cylinder where the immobilizer antenna is. you can use a zip tie or tape to hold it tightly, zip tie being better.

if you can't get your to work at all(as far as placement goes), you could try the DEI 555H which should interface with the imobilizer unit directly without the key.