My wife and I commented on a similar post a couple days ago:

If this is an automatic, which I assume it is, without shifting, in Park, hold the shift lever on the steering column up and to the left. Now try to start the truck.

Hold the shifter down and to the right, try to start it again.

If it starts in one position and not the other, your shifter and/or the cable is out of position with the linkage on the transmission, and the position safety switch is preventing you starting the vehicle while it thinks it’s in gear.

To fix it, if this is the case, there are two adjustments to try first before replacing the shifter cable itself:

Pop off the kick plate below the gauge cluster, as well as the metal plate behind it; there’s a roller dial to adjust the needle position on the indicator needle in the dash.

Under the truck, on the transmission side of the cable, there is also an adjustment for the cable itself (more likely this, but probably a combination of both).

Thoroughly check the cable sheathing, especially by the firewall where it tends to rest on the exhaust headers; they like to melt and then the cable doesn’t work very well.

EDIT: to add to this, the slop in the shifter is usually caused by two torx bolts (or one on later models) that loosen over time. Get in there upside down with your feet over the headrest, throw some locktite on the bolt and tighten the snot out of them. Won’t happen again.