The .mp4 extension is just a container. The actual video inside could be encoded with H.264, H.265 (HEVC), or AV1. If your media player shows a black screen but plays audio, you need to update your video codecs or use a versatile player like VLC Media Player. 3. File Corruption
Because this file is labeled as part five ("-5-"), the video may not play correctly if it is part of a split RAR or ZIP archive and parts 1 through 4 are missing. Ensure you have downloaded the entire sequence. 2. Codec Compatibility