I have an ’04 Expedition. Started fine all morning. Let it sit about an hour or so, went out to go to work, turned the key, everything comes on but it won’t even turn over. Starter or solenoid aren’t making a sound. There is a buzzing type alarm coming from what sounds like the passenger floorboard, which I’ve never heard before.
Most likely a weak or dead battery. If the lights on the dash go dim or completely out when you hit the key it would indicate the ignition switch is working. The radio and lights do not require much amperage to operate. This may give you a false sense that the battery must be good, but it probably isn’t. Once you have fully charged and load tested the battery or replaced it, it still has the same issue a test may be necessary. Check for battery voltage at the “S” terminal on the starter while someone holds the ignition key in the “START” position. If you see battery voltage, replace the starter. If you do not see battery voltage, trace and repair/replace as needed.