Ok if it's genuine Ford/Rotunda it should work. There are a lot of knock-off chinese ones put there that claim to be genuine but are in fact counterfeit. If the price was super low, it's probably counterfeit.
This is the procedure from the Workshop Manual; is this what you're trying?
Key Programming Using Two Programmed Keys
Programming
NOTE: This procedure works only if 2 or more programmed keys are available.
NOTE: This procedure works only if the customer spare key programming is enabled.
NOTE: When programming keys, the RKE transmitter and the PATS portion of the key are programmed at the same time.
- Insert the first programmed PATS key into the ignition lock cylinder and turn the ignition lock cylinder to RUN (maintain the key in RUN for approximately 3 seconds).
- Turn the first key to OFF and remove the key from the ignition lock cylinder.
- Within 10 seconds of turning the first key to OFF, insert a second programmed PATS key into the ignition lock cylinder and turn the key to RUN (maintain the key in RUN for approximately 3 seconds).
- Turn the second key to OFF and remove the key from the ignition lock cylinder.
- Within 10 seconds of turning the second key to OFF, insert the new, unprogrammed PATS key into the ignition lock cylinder and turn the ignition lock cylinder to RUN (maintain the key in RUN for approximately 6 seconds).
- NOTE: See the Owner's Literature for maximum number of keys that can be programmed to the vehicle.
Repeat steps 1-5 to program additional keys.