It sounds like either the shift linkage cable has broken or came disconnected. Secure the vehicle first so it can't move. Have a helper get in the truck with the parking brake on and their foot on the brakes.
Crawl under the truck and locate the shift linkage cable where it attaches to the transmission. See pic 1 below. Have the helper shift through the gears to see if there is movement in the shift lever on the transmission.
Let me know what you find,
See pic below.
Sunday, June 13th, 2021 AT 10:02 PM