Can not get truck to start only a clicking noise

I had to replace my flexplate and starter on my 2006 f150 5.4L v8. To do so I had to pull my transmission out of the way so I could reach the flexplate and replace it. After I replaced the flexplate, the starter and put the truck back together I can not get the truck to crank or start. Only a clicking noise when I try to start the truck. I have a good battery and headlights. The dash lights come on also can here the fuel pump turn on. The only thing that it is doing is not cranking or starting. And all I hear is a click when trying to start the truck. Please can anybody help me figure out what could be going on?

Only a clicking noise

Step by step No Start diagnostic chart

A rule of thumb for only a clicking noise when turning the key is repeating clicks (click, click, click, click, click) are an indication of a weak/dead battery. One soft click is an indication of a loose/poor connection. A misconception is thinking the battery is good/charged because you see dash or headlights. The lights or radio draw less than 10 amps to operate while a starter may draw up to 250 amps. Meaning a junk battery still has enough juice to make the lights and radio work but not enough to make the car start.

What Now

So with all that being said. Charge the battery fully before testing. This may be the cause of the problem of only a clicking noise. If the issue still occurs check both connections at the battery to be clean and secure. Check the ground connection and positive connections at the starter. Then test, try to start. Problem still there? While someone holds the ignition key in the “START” position check for battery positive at the “S” terminal on the starter. If you see battery positive at the “S” terminal and know you have good battery positive and negative connections, replace the starter. If yo do not see battery positive at the “S” terminal you will need to trace the wiring back through the gear selector switch and then to the starter relay.