macbook left shift key not working

This resource explains how to clean your keyboard on a 2015 or newer Macbook and MacBook Pro. There is a hyperlink at the bottom for cleaning other Apple products. I would recommend trying to clean it first and if the issue persists to then visit an Apple Store or Apple Authorized Service Provider.

I agree with AppleCard4Lyfe. Try cleaning the keyboard, also try and pressing the key when you'd removed the key itself and then you'll get the idea if key if not working or its was dust. Hope it helps. These are small secret hacks that you should know.

Thanks