Tom got a notice from Microsoft to update Windows 10, but now it won't recognize his keyboard, so he can't log in. Leo says that Tom can eliminate the keyboard as the problem by trying it with another computer. But likely, the update deleted or corrupted the USB drivers. Log into safe mode and see if it works. If you can at least get into the BIOS setup, then you know it isn't the keyboard.
That would mean you can fix it by reinstalling Windows. Download the Windows Media Creation Tool and install it onto a USB Thumbdrive. Then start it up and try to repair Windows. If that doesn't work, reboot and install it from scratch.