Dirt on top of plugs - can't get socket on

That’s what I would try if I ever encountered this particular issue - however I haven’t had the opportunity - and I’ve have replaced a BUNCH of spark plugs on MANY F-150 pickups - including the 2004’s.. That rubber boot on the coil is also supposed to keep foreign particles out of the spark plug tubes.. You may be having difficulties with the selection of tools you’re using - perhaps the socket isn’t actually reaching the spark plugs in question. It is always convenient to know exactly WHICH engine the vehicle is equipped with Good luck!