Hi Welcome to the forums! Check fuel system pressure using computer diagnostic tools (there is no port to attach a gauge). The 5.0L engine has a 3 stage high pressure fuel system (similar to a diesel engine) with over 2000psi on fuel rail. If it starts after sitting for a while, injector leakdown is a possibility. You can also run fuel prime routine in diagnostic computer to see if pump runs.
Another thing to check is loss of coolant, which is a sign of potential overheating/leak.