Since diagnostics already did not help, use the Surface keyboard checks that separate a Windows problem from a hardware problem:
- Open the Surface app.
- Expand Help & support.
- Check for updates.
- If updates are available, select Check for updates and install them.
- Confirm whether the keyboard is still electrically responding.
- Press the Caps key and Fn key a few times.
- If the LED lights do not turn on, that points to a hardware issue.
- If the LEDs turn on, continue with the UEFI test below.
- Test the keyboard in UEFI.
- Turn off the Surface and wait 10 seconds.
- Press and hold Volume Up.
- While holding Volume Up, press and release Power.
- Keep holding Volume Up until the UEFI screen appears.
- Try the arrow keys there.
- Interpret the result.
- If the keys work in UEFI but not in Windows: the issue is likely Windows/software related. Use Start > type reset > Reset this PC > Keep my files > Cloud download. Note: this reinstalls Windows, keeps personal files and apps that came with the PC, but removes apps, drivers, and settings changes that were added later.
- If the keys do not work in UEFI: that points to a hardware problem.
- If the keyboard still fails:
- In the Surface app, select Get help and describe the problem.
- If the LEDs do not turn on or the keyboard fails in UEFI, submit a service order for the device.
If the problem is only that typed characters do not match what appears on screen, also check Start > Settings > Time & language > Region & language and make sure the keyboard input language matches the display language.