Microsoft Security Essentials error 0x80240022

I have relied on Microsoft security essentials to protect my PC for years, but a few days ago, I ran into an issue I simply cannot resolve.
I spent some time searching through the Microsoft support pages for a fix, but nothing worked.

Down in the system tray, I see this message: Microsoft security essentials / computer status: potentially unprotected - Update definitions
Every time I click on "Update definitions" I get this error:

Virus and spyware definitions cannot be updated.
The application is unable to search for virus and spyware definition updates. Please check your internet or network connection and try again.

I reached out to their support department, but they just keep redirecting me to various webpages that offer no actual solution to my specific problem.
Does anyone know how to handle this?

..you tried any of those fixes yet??
like, maybe open up an admin CMD prompt and run sfc /scannow just to see if it can patch things up?

I ran the scan and it claims there aren't any errors at all
The issue persists
It makes no sense why the update won't go through when it keeps prompting me to do it

What if you just tried a clean reinstall of the program?

It’s just some ancient software running on an even older OS. You really think they stopped supporting it by accident?