2004 ford f150 instrument cluster lights flash when turn key to on/start and truck will not start any ideas

2004 ford f150 instrument cluster lights flash when turn key to on/start and truck will not start any ideas:?

You have "bulb prove out" sequence verified, thats expected, but you need to check the gearshift position, step on the brake, etc.
You need good battery cables and connections, you also need power on the start enable wire.
The resulting tests can be begun with verifying connections, testing the available voltage and state of charge, a look at a wiring diagram can be very helpful because the starter relay on these can be back by the firewall and covered up.
First I would see if I had power to the enable wire during crank, see if the solenoid is loose, then go up and see if they hid a relay under a plastic cover. Tap on it. If a helper can start it during this, drive straight to the part store and show them what part responded to the Tapping. That could be your often misdiagnosed problem. It can also simply have an open and need replacing for that. There won't be any power down at the starter on the B+ cable unless this relay sends it. There are other systems in play but if you haven't fixed it yet, the problem can be diagnosed with the pinpoint tests.