I have a newly purchased 13 '' MacBook Air 2015, and now the function keys that must control the volume up / down / silence and brightness do not work. When I press any of them, I get an error sound and nothing happens. Things I've tried: -Mark / unmark "use the F1, F2, etc. keys as standard function keys". Even when checked, pressing 'fn' and the function key does not work. -Display the shortcut keys for the Mission Control (when it is activated, the F10 key will show the desktop) -Zapping PRAM - Beginning in safe mode -Restate OSX keyboard shortcut settings to default - External monitor unplugged and mouse. -Reset SMC -Proved external keyboard and same behavior All software / OS updates are installed Running OSX Mojave 10.14.4 I would appreciate any help! Thank you!