2009 Ranger - 4.0

Bought the truck just over a month ago and it was bought knowing it needed transmission work. Before I bought the truck I made sure it started, which it did. Fast forward to today, I have completely put the trans back together and put it back into the truck. When trying to start it the first time, the engine cranked but would not start. After taking out the keys and trying again, it would not even turn over, then it would randomly turn over one more time and it has not turned over since. My dad noted that when we turned the keys and tried to start the truck that the headlights were not dimming (i.e., the battery was not the problem). I have no idea what the problem could be. We were thinking that possibly the starter could have a problem but it didn't seem like it was struggling during the first turnovers. The battery we were using was sketchy but it seemed to be working. Going to be using a code reader tomorrow.
If anyone could help out or has any questions please help a man out

Thanks!

 

Welcome to the forum

Manual or automatic transmission?

There is a Neutral Switch that prevents starter motor activation while "in gear"
On a Manual its on the clutch pedal
On an Automatic its on the Drivers side of transmission, called DTR sensor

2009 Ranger will have PATS(passive anti-theft system)
On the dash there will be a THEFT light
When you turn the key ON the THEFT light should come ON and then go OFF, Key passed the PATS test
If it flashes rapidly it means PATS is activated(key did not pass the test) and will not allow startup, no starter motor and no Fuel injection

Low battery voltage can trigger PATS when you try to start engine

 

I wouldn't rule out the battery entirely, try jumping it?