The Ford proximity key with FCC M3N5WY8609 commonly known as the "paddle" key has two options that work on different vehicles and that are not interchangeable, with either a high security keyway or a regular keyway.
Here's the tricky part - both emergency key blades fit in the slot so often these blades can be wrongly placed in the incorrect key. How to know which key has which blade? Check the part number!
Ford Part Number CJ5T-15K601 requires a high security key blade.
This number can be found in the top right corner under where the key blade typically lies.
Ford Part Number BT4T-15K6012 requires a regular key blade shown below