Make sure to click Keyboard shortcuts on.
In the General tab, scroll down to Keyboard shortcuts.To enable it, open Gmail, click the gear icon and then click Settings.Out of the box, this feature is disabled. The first thing to do is enable keyboard shortcuts.SEE: Serverless computing: A guide for IT leaders (Tech Pro Research) Enable keyboard shortcuts
With Gmail, you can not only enable keyboard shortcuts, but create custom combinations to make your experience as efficient as possible.