Keyboard is not working on one user account but works on others

Only one user account on my mac cannot use the keyboard. All other accounts including the admin works fine. But after my son signs in to his account (using the keyboard to type his password) the keyboard is no longer detected by bluetooth. The mouse works fine and it seems as though the keyboard actually loses power too because the caps lock button does not even light up anymore. However, the one-screen display pops up whenever we unplug or plug in the keyboard, and shows the correct status, it just doesn't recognize any keypresses.