Keyboard and mouse not recognized after boot-up!

Hi, have you checked your Device Manager for yellow triangles for those devices? Are drivers installed?

If they are, check if they have been recently updated in Device Manager.
Check if you have the option to roll back the driver.

Please post a screenshot of your Update History - to which update are you referring?
To post a screenshot please use the icon above your post to the left of the video icon

Your shutdown sounds strange.
Try from an admin command prompt running
SFC /SCANNOW
and report the result.

If all this happened at the same point you might consider using a System Restore point, assuming you have System Restore enabled and useful recent restore points.

Sorry, should have suggested the wired option in the hope you had one.. or could borrow one.

Another option you might have is to boot your PC from either
- a Win 10 boot disk
or
- Kyhi's boot disk available from the top of the Software and Apps section.

Try your keyboard and mouse with those.

If you had System Restore enabled, using the Win 10 boot disk, then via Repair your computer, navigate through the Advanced Startup options to System Restore and try that.

Plugged in the new *wired* keyboard and mouse, rebooted a couple of times, but no luck---neither the wired keyboard nor the wired mouse are functioning. The wired mouse *was*, to some extent, recognized by Windows, in that Windows popped up the typical message window indicating that it was setting up the mouse and a second window indicating that the mouse was "ready to use". There may have been some similar messages when I plugged in the wired keyboard, but if so, I didn't notice them. (Edit: After making this post, I moved the keyboard plug to another USB port to verify that Windows would acknowledge that a keyboard had been plugged in, and it did acknowledge that, but the keyboard is still not working.) Regardless of those Windows messages, for the mouse, the mouse is not working at all, there's no pointer displayed on screen, and the mouse and the keyboard are not working.

So, it's on to recovery mode and System Restore. I'll be trying either a USB thumb drive with the Win 10 install files on it or an Active@ Boot Disk disc. Probably try the Active@ Boot Disk first. I don't know how the boot sequence is configured in the BIOS (or UEFI, now, I suppose) of my Dell PC---that's something that I knew well in earlier versions of Windows, but haven't looked at on my Win 10 machine---but hopefully the PC will boot to one of these two media and not just go straight to the Win 10 desktop.

EDITED: 3:25PM Eastern

It's either that or restoring recent backups, most current first, until you get back to working. Then, you can apply updates one at a time until you figure out which one breaks your system (then block that one from installing). Sorry for your troubles!
--Ed--

Do you have the ability to get into the BIOS when you start booting? I'm afraid you're going to have to manipulate the boot order explicitly that way and force it to boot from the USB flash drive. Have you tried remoting into the affected PC from your wife's machine (must be running Win10 Pro, Education or Enterprise, tho...)? If you can remote in, you should be able to get into the startup controls and tell it to boot into BIOS following the next restart (Start --> Settings --> Update & recovery --> Recovery --> Advanced startup --> Restart now).
Cross your fingers, and hope remote access works. That will let you drive the OS and get yourself moving down the path to recovery.
HTH,
--Ed--