Thank you!!! I cannot begin to tell you how many pages of fixes I have been through, MS or otherwise. I spent days trying to get WU to work on my mom's old Windows 8.1 (granted, it hadn't been updated in 2 years, but still...) Hours and hours of searching and trying so many different solutions. I love the sites that say, "THIS WILL WORK, I GUARANTEE!" and it doesn't. Or it calls for changing a setting that does not exist. Then there are the MS KB pages with dead links. Or it says, "Sorry, if that didn't work you need to reinstall Windows." Like that's the go-to solution. And Lord knows how many error codes there are. It's hard to imagine that in 2017 there isn't a way that MS can truly diagnose and fix WU issues...not to mention how amazing it is that there are so many. There must be more questions/pages/solutions on this than just about anything.
At any rate, your solution worked perfectly.
Now if I could only get WU working on an old W7 SP1 that hasn't been updated in 2 years...