I'm using Sexymap for my minimap (shown on the top right of my UI screenshot) and although the zone is enabled, it is not showing and I'm not quite sure why.
Open the options, and expand the + on the left.
Profiles, click the Reset Profile button.
That may be per character, or per account I am not sure, but it will at least prove whether or not that is an issue with the settings, or something else intefering.
Either that or log out from the game completely (to the desktop), then enter the WTF\Account\YOUR_ACCOUNT\SavedVariables folder in your WoW directory, and delete the SexyMap.lua and SexyMap.lua.bak files.
You came here asking what was a fair question.
You followed our instructions, and eventually figured out the problem yourself.
Not what I would call dumb.