Spare key opens car via blipper buttons but won't start car

[rokgod]

Immobiliser kicks in after changing key fob body

Hi. I’m new to the site having just bought my first MX5 NC. I bought a new key fob body and swapped the blade and electronics from the old key fob. The doors and boot unlock no problem but when I try to start the car the immobiliser drops in. Any suggestions on what the problem is and how to solve it?

Might help, at the least it shows where the chip is.