How do i re-attach the up arrow key on my hp pavilion dv7-6143cl? It has come loose but all of the parts are still intact.

Hello thf you look closely at the place where the key fits examine it and look to see if there are any broken tabs if not the key should simply press back in it does take some pressure and you should feel a snap when it is locked in place
Now if it does not then the key itself may be faulty which means you can get a another key from a old key board or just replace the keyboard itself they really are not too expensive ok
Hop this helps
Best regards Michael