Hello I'm Chris a Ford Certified Electrical/Engine Specialist.
Thanks for asking your question. I am eager to get your vehicle back up and running correct, I am here to help you out for a small fee far less than a dealership, so if this information is of aid PLEASE PRESS ACCEPT and help me out financially. Please reply if further discussion is needed.
It could be many things including a seized engine. Here is the starter circuit. You have have to verify power and ground where needed. Normally crossing the relay will by pass everything and make the starter turn the engine over. To see if the engine is seized you can turn the crank pulley with a socket and ratchet on the center bolt. You can also bypass the electrical even farther and connect battery voltage to the starter solenoid and make the starter try to work. If this fails and the engine will turn over then assume the starter is bad.