so this has me a little stumped.
There are 3 antenna to receive the keyfob ID. One near the driver door, one near the front passenger door, and one at the rear bumper.
if the presence of the keyfob unlocks the door, then shouldn't it also permit the vehicle to be started?
i had the key not detected problem in the past, replaced the fob battery, but still had the problem.
A workaround was to slap the fob between my hands.
The permanent solution was to remove the fob battery, expand the four fingers that contact the battery, so that they put greater pressure on the battery, and then close it all up.
It seems the fingers were just not making good contact with the battery, and after expanding them (be careful not to break them) the problem has not occurred since.