Quick check: Run the related device test and keep it open while trying these steps.
Focus the test area
Click the keyboard test area before pressing a key. The page shows the key name, its physical code and a press count. Try a known working key first to confirm the area has focus. Then press the suspect key several times. A count that increases for the good key but never for the suspect key suggests the browser is not receiving that press.
Understand the two labels
The Key value reflects the current keyboard layout and modifiers. The Code value identifies the physical key position more consistently. For example, changing a language layout can change the character shown for a position without changing its hardware code. If the key triggers the wrong character, check the selected Windows input language before assuming the switch is broken.
Check the easy hardware causes
For an external keyboard, reconnect it or use another port; for wireless models, check the battery and receiver connection. Clean around a stuck key using the manufacturer’s safe cleaning guidance. Do not pull a laptop keycap without instructions for that model. Try another keyboard on the same computer, or this keyboard on another computer, to identify which side the problem follows.
Remember the browser limit
Windows, the browser and extensions can intercept some shortcuts before this page sees them. Media and special function keys may not produce a normal keyboard event. If ordinary letters work here but not in one game, examine that game’s bindings. This test reports events delivered to a web page and cannot measure switch actuation force or electrical reliability.
After each change, test the device again. Change one setting at a time so you can identify what helped.
Further reference: Official device or browser documentation ↗