A S D Keys not working at all
A S D keys are not working to type password in Mac Book air
Question marked as
If you have one available to you, try using an external keyboard and seeing if the keypresses register. If that works, then unfortunately you need to take your MacBook to get serviced.
Alternatively, your Mac may be showing a low battery alert that you can’t see. Connect your Mac to an electrical outlet or connect an external keyboard to your Mac to see the alert.
I have also heard of a solution involving resetting the PRAM on your device. The below link will assist in that process. Please note that this wouldn't apply to you if you are using a MacBook Air on Apple Silicon.
Reset NVRAM on your Mac - Apple Support