@Fruit Bat - Yes, I looked at the links. The first said it was being "retired", which is exactly what I wrote in the original post. The second is the old download page that clearly says "The Guardian is currently not available." Does it say something different for you?
@MJS WARLORD - Again, thanks for the reply but it doesn't help me. I appreciate the suggestion but I am already aware of The Guardian website. I want the app. It wasn't an app that I ever recall having an executable installer for; it was all installed via Microsoft Store, so there's nothing I could have saved (I don't think so anyway.)