How to repair up arrow button

Those buttons can usually be removed by carefully prying them up with a screwdriver. If you remove it, look in the hole for a piece broken off the button. In the bottom of he hole, push the plastic piece and see if the "up arrow" function works as it should. If so, the button piece itself is probably broken. I have had good luck with hot glue, but not to reattach the broken piece. I have used hot glue to replace the small piece that sometimes breaks off of the button. With a hot glue gun, put a small drop on the broken button. Let it dry. You might have to add more glue, one drop at a time, until there is enough built up to reach the bottom of the hole where the button goes.

Don't glue the button into the hole. Don't reinstall the button until the ball of hot glue is dry and hard. The broken off piece of the button cannot be glued back on effectively.

If you cannot make the button function work with a small screwdriver, you will probably need to replace the keyboard.