Auto Start / Immobilizer Bypass Issue

[ny2003ses]

I now have an 03 Taurus SES. Tried reinstalling my auto start from my 05 Taurus SEL however having trouble with the DEI Immobilizer.

Scenarios:

No key in ignition:
When I activate auto start, it goes through the process and as it attempts to start the car however at the point it would engage the starter, there is nothing... dead

With key in ignition but not turned:
Auto start works as desired

Without auto start use:
Simply using the key to start the car - nothing, car is dead as the immobilizer bypass seems to be trumping the key

Fully removed auto start and immobilizer bypass:
Keys start the care without issue

I have a spare key inside the immobilizer box which I know works to start the car as I've tried it before the install.

Any ideas from all the techs out there?

Thanks in advance!
Jeff