What is the of the video you are trying to convert? Do you have FFmpeg already installed on your system?
: Explicitly declare the path. Open your terminal config or application script and manually append your local system file path to the engine (e.g., C:\Program Files\MKVToolNix\mkvmerge.exe on Windows systems). Error: Permission Denied (publickey) or Fetch Failures nwoleakscomniks2mkv install
If you are on a fresh install of Windows, you might need the "Visual C++ Redistributable" packages. Final Thoughts What is the of the video you are trying to convert