After a recent inexplicable problem on my MacBook, in which macOS would complete loading but never get past the blank screen before the Desktop appeared, I had to revert to a clone. (Even reinstalling macOS didn’t work.) I then upgraded to Mojave. Somewhere in there, an important piece of macOS “fell out,” metaphorically.
Apple added the concept in 10.13 High Sierra of a “secure token” to the first account created in macOS on installation or after upgrade as part of the process that allows you to use FileVault. There’s almost no information about this feature, and there’s no way to determine from macOS’s graphical features whether an account has it set.