My work was selling off old Dell E5470 laptops minus the hard drives for $30.  I picked up two of them and a couple of new hard drives from the local store.  Using a Windows 10 recovery USB and they were back in business.  All good except one of the laptops the keyboard didn't work

After a bit of googling, I have tried the following:

1) Drivers - Uninstall and Restart (Windows will re-install).  No luck.  Scanned for hardware changes - no luck.

2) Updated Drivers and Bios.  Went the Dell website and updated all the relevant drivers and BIOS to the most current.  no luck.

3) Swapped Keyboards between the two laptops.  The benefit of having two machines the same was that I was able to determine the problem is not the keyboard hardware itself.  After swapping them, the problem stayed with the laptop, not the keyboard.  The keyboard worked fine on the other laptop.

4) Safe mode - Tried loading Windows in safe mode, no luck.

5) Troubleshooter Keyboard - Ran the Windows troubleshooter app and it did not detect any issues.

I am at a bit of a loss as what to try next.  I suspect that there might be another hardware issue not directly related to the keyboard itself.  

I can use and external keyboard, as this post proves, but it would be nice to get the original keyboard functioning.

I would appreciate any other suggestions.