Perhaps this is well known but I ran into this today when I used a set of keys that are not normally used. I thought it was odd they didn’t unlock it but I usually use the buttons on the door so I figured I would do the battery in the fob later. Jump in and it would not recognize a key was inside. In the center console there is a pocket that if you place the key in when it is dead it will recognize it. This is in a Lincoln but Ford’s have a similar thing in the console and I have heard others have a pocket at the bottom of the cup holder under the mat.