Have you altered the missionscripting.lua?
From the readme:
2. Open the file "DCS World\Scripts\MissionScripting.lua". Add two minus signs in front of line 16 "sanitizeModule('os')" and line 17 "sanitizeModule('io')". The code block from line 16 to line 20 should then look like this:
--sanitizeModule('os')
--sanitizeModule('io')
sanitizeModule('lfs')
require = nil
loadlib = nil
This modification has to be repeated after each update of DCS World, as each update reverts the file back to its original state.
WARNING: This modification will allow the execution of LUA code included in any downloaded custom mission that is potentially harmful to your system. Modification at your own risk.
Also, run the game as an admin, I have to do that to make it run