One who does not understand computers, or one who harbors a deep-rooted dislike for computers or the Internet.
From the X-Men term "flatscan", a derogatory term for non-mutants. As the mutants considered themselves the next step in human evolution, "flatscans" were those who would be left behind as the world progressed. A similar fate awaits those who dislike or cannot comprehend computers, and the cyber community adapted the term to mean non-cyber rather than non-mutant.
Flatscans generally need to call tech support for such complicated steps as opening Microsoft Word, and never remember to check their email.