2020-02-07 09:20:07.263 INFO    LuaNET: VRK - Mission Loaded: C:/Users/Kenny/Saved Games/DCS/Mods/tech/DCE/Missions/Campaigns/FA-18C Battle Group Delta_first.miz
2020-02-07 09:20:07.268 INFO    TACVIEW.DLL: Tacview Flight Data Recorder 1.7.1 Loaded
2020-02-07 09:20:07.268 INFO    TACVIEW.DLL: Config={bookmarkShortcut=0, clientTelemetryPassword="", compressionLevel=1, dataRecordingEnabled=0, debugModeEnabled=0, hostTelemetryPassword="", playbackDelay=600, profilingPeriod=600, realTimeTelemetryPort=42674, recordClientsSessionsEnabled=0, remoteControlPassword="", remoteControlPort=42675}
2020-02-07 09:20:07.269 INFO    DCS: Screen: mission_offline
2020-02-07 09:20:07.269 INFO    Dispatcher: precache units resources in slots
2020-02-07 09:20:07.347 INFO    Lua: Lua CPU usage: metric: average mission loading: 23.3860 %
2020-02-07 09:20:07.347 INFO    Dispatcher: loadMission Done: Сontrol passed to the player
2020-02-07 09:20:21.916 ERROR   DCS: Mission script error: : [string "C:\Users\Kenny\AppData\Local\Temp\DCS\/~mis0000291D.lua"]:13: attempt to index global 'os' (a nil value)
stack traceback:
[C]: ?
[string "C:\Users\Kenny\AppData\Local\Temp\DCS\/~mis0000291D.lua"]:13: in main chunk
2020-02-07 09:20:22.793 INFO    EDCORE: (wcTanker)enterToState_:0
2020-02-07 09:20:22.793 INFO    DCS: wcTanker::onEvent:4
2020-02-07 09:20:22.793 INFO    EDCORE: (wcTanker)enterToState_:1
   
I got that mission script error after i start the mission.  
I can play the first mission if i ignore this message. but i cannot proceed to second mission. 
any idea to solve it? 
i checked all files are in correct location.