Have a look to see if something is lodged between 2 surfaces, lets say between the truck bed and the tailgate, maybe something lodged in the tailgate locking mechanisms, clean it out if something is lodged in there, lets say a small piece of wood.
Also check the moving parts which is connected to the locking mechanisms for the tailgate, something could be seized, maybe needs replacement or needs to be freed up with penetrating fluid and once its moves freely spray white grease on it.
Also make sure the tailgate is not damaged in such way that it prevents it from properly closing.
If you have looked at it, and its all clear then the tailgate maybe just not working and needs to get the tailgate inside moving parts, repaired or replaced to get it functioning again.
Answers & Comments
Have a look to see if something is lodged between 2 surfaces, lets say between the truck bed and the tailgate, maybe something lodged in the tailgate locking mechanisms, clean it out if something is lodged in there, lets say a small piece of wood.
Also check the moving parts which is connected to the locking mechanisms for the tailgate, something could be seized, maybe needs replacement or needs to be freed up with penetrating fluid and once its moves freely spray white grease on it.
Also make sure the tailgate is not damaged in such way that it prevents it from properly closing.
If you have looked at it, and its all clear then the tailgate maybe just not working and needs to get the tailgate inside moving parts, repaired or replaced to get it functioning again.
Hope this helps, have a nice day.