What I think you did is set your "global settings" to never rather than setting individual units. Global settings are activated by pressing the "D" key when no unit is selected and they will take priority over individual settings unles the individual setting is
more restrictive.
What you need to do is access the global settings again, change the desired category to long, or any other you choose, than select units individually to enter a more restrictive setting.
Typically when I start a scenario I will set all globals to long then individually tweak every unit on the map... but then I am a bit of a control freak. :rolleyes:
The most important thing to remember is global settings always take priority over individual unit settings
unless the individual settings are more restrictive.
Hope that solves your mystery.