First, there can be issues with debris cluttering the keyboard. If the debris is externally causing issues, wipe the keyboard with a rag and/or carefully remove the debris with compressed air. If the debris is stuck under the key, follow the guide for how to remove the keyboard to access the debris. If you find there is not debris preventing the keyboard from working, there may be a problem with the software on the laptop. Usually performing a factory reset will fix this issue.