This error means FFmpeg can't handle the codec of the input stream. Common cases involve unsupported formats like vp8, or container issues like .webm. You can resolve this by editing your transcode profile to include compatible codecs such as -c:v libx264 -c:a aac. Also make sure your FFmpeg version is compiled with libx264 and libfdk_aac support. Use ffmpeg -codecs to list available options. In some VPS environments, codec support is limited due to how FFmpeg was compiled.