Face ID Not Working [Fixed. Please see the approved answer for details.]

It seems everyone having this issue reset their settings for some reason. I haven’t read one post on any forum, and I’ve asked on several of them, about this issue from anyone who didn’t reset their settings. This is the only forum where I’ve even seen this mentioned. I was hesitant to install 8 because of the posts here but I have now installed 8, and deleted 7, on my phone with no issues. Face ID works perfectly every time. That suggests to me that there is an iOS issue for those who did this settings reset. Which also suggests that the solution will have to come from an Apple update with Agilebits and other developers working with them.