5590 lost its Windows key?

Connect the system to the Internet -- if Windows was activated before, the system should pick up the entitlement from the Microsoft activation server.

Besides the embedded license key, if your device has been activated, Microsoft also kept the hardware ID associated with the license.  It does not matter how many times you perform Windows reinstallation, the device will be activated once it's connected online.

If your device has issue with license, select activation troubleshooting and it may resolve itself.

The computer is on the internet.

The issue is that the Windows Activation Key that's embedded in the BIOS is somehow . . . GONE. 

Sometimes that happens when the computer has the motherboard replaced, but this computer never had any warranty work on it. 

I ran the command line and powershell commands that pull the Activation Key from the BIOS and display it, but both are displaying a blank key. 

I was hoping there was a BIOS setting that had been switched that might have prevented the key from being accessible, but since I restored the BIOS to factory defaults, that's not it, either. 

The computer is out of warranty, and I don't have the receipt from when the device was purchased, so Microsoft and Dell won't help.

Looks like I'm going to need to buy a new Windows license. If Dell just shipped with those stickers with the Windows keys, I'd still be in business. 

Older systems that were allowed free upgrade from Windows 7 COA to Windows 10, they all don't have any Windows license key on motherboards.  The Windows digital license were issued based on hardware ID.