Well Dust, dirt, hair, and other debris can fall into the keyboard over time and obstruct a key's movement or interfere with its circuitry. Try removing the key that isn't working, and clean the area under and around it. And also check for [link|https://wethegeek.com/logitech-keyboard-not-working/|outdated keyboard driver|new_window=true] can also cause the this issue as well so I will suggest you to check your keyboard driver if it is outdated then updated the driver.