I installed the FFMPEG library as per instruction on the wiki, using the Audacity 3.1.3 and FFmpeg 2.2.2
13:28:47: User-specified path = ‘X:\Ffmpeg For Audacity (2)’
13:28:47: Error: Failed to load shared library ‘avformat-58.dll’ (error 126: The specified module could not be found.)
13:28:47: Error: Failed to load avformat-58.dll (error 126: The specified module could not be found.)
13:28:47: Error: Failed to load shared library ‘avformat-57.dll’ (error 126: The specified module could not be found.)
13:28:47: Error: Failed to load avformat-57.dll (error 126: The specified module could not be found.)
13:28:47: Error: Failed to load shared library ‘avformat-55.dll’ (error 126: The specified module could not be found.)
13:28:47: Error: Failed to load avformat-55.dll (error 126: The specified module could not be found.)
13:28:47: Error: User-specified path does not contain FFmpeg libraries.
13:28:48: Error: Failed to load shared library ‘avformat-58.dll’ (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load avformat-58.dll (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load shared library ‘avformat-57.dll’ (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load avformat-57.dll (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load shared library ‘avformat-55.dll’ (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load avformat-55.dll (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load shared library ‘avformat-58.dll’ (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load avformat-58.dll (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load shared library ‘avformat-57.dll’ (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load avformat-57.dll (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load shared library ‘avformat-55.dll’ (error 126: The specified module could not be found.)
13:28:48: Error: Failed to load avformat-55.dll (error 126: The specified module could not be found.)
I also tried on installing the library on both Program Files and Program Files (x86) and the results are still the same