You really need to provide more explanation.
However, that said, your keyboard may be broken.
Keyboards work by using a matrix of wires that uniquely identify the key(s) being pressed.
If the keyboard has been physically broken then you need a new keyboard.
However, if the keyboard works on another computer then the keyboard drivers on the "Only Half of Shift Key Working" computer may need to be reinstalled or replaced.
Test the keyboard on another computer and see if you can provide some additional details accordingly.