Look back at your "Saved Messages" or the specific chat/channel where you downloaded it to see the original caption or context.
If the video won't open in your default player (like Windows Media Player or QuickTime): 5_6204072876023219776mp4
Go back to the Telegram app and ensure the progress circle is finished. Look back at your "Saved Messages" or the
Use the Files by Google app or MX Player on Android to bypass gallery indexing issues. 3. Fixing Playback Issues 5_6204072876023219776mp4
Use (Free/Open Source) to re-encode the video into a "Constant Framerate" MP4. This usually fixes any sync or compatibility issues common with mobile-shared videos.
It supports almost every codec and can often play files that appear "corrupted" or have Telegram-specific encoding issues.