Since the keyboard works only after repeated software diagnostics and the hardware has already been cleaned, updated, and hard-restarted, the supported next step is to isolate Windows from hardware and then repair Windows if needed.
- Confirm whether the keyboard works in UEFI
- Turn off the Surface and wait 10 seconds.
- Press and hold Volume Up, then press and release Power.
- Keep holding Volume Up until the UEFI screen appears.
- Test the keyboard there using the arrow keys.
- Interpret the result
- If the keyboard does not work in UEFI: this points to a hardware failure, and the next step is to submit a service order.
- If the keyboard works in UEFI but fails in Windows: this points to a Windows/software issue.
- If it is a Windows/software issue, use the supported repair path
- Go to Start, type reset, then select Reset this PC.
- Select Reset this PC > Keep my files > Cloud download.
- Follow the prompts.
This reinstalls Windows, keeps personal files and apps that came with the PC, and removes changes to settings plus apps and drivers that were installed. This is the documented path when the keyboard works correctly in UEFI but not in Windows.
- Before resetting, check updates in the Surface app one more time
- Open the Surface app.
- Expand Help & support.
- Select Check for updates to open Windows Update and install available updates.
- If needed, run the Surface Diagnostic Toolkit from Start and follow the on-screen steps.
- If using a custom or clean Windows image
- The keyboard may need the latest Surface driver package installed manually.
Given the symptom pattern, the most direct permanent fix supported here is: test in UEFI first, and if it works there, repair Windows with Reset this PC using Keep my files and Cloud download.