Failure to extract natives is the result of Lunar Client not being able to access specific game files. This is usually the result of trying to open two instances of the game or the old game process not being terminated properly.



Instructions 


Step 1: Open Command Prompt

  1. Press the Windows key to open Search.
  2. Type in "cmd", then press the "Run as administrator" button.



Step 2: End Minecraft process


  1. Type in the command "taskkill /im javaw.exe /f", then hit the Enter key.
  2. Close Command Prompt.




Restarting your computer will also have the same effect. However, it may take longer depending on the speed of your computer.