Use a public CDN link
Discord attachment URLs (cdn.discordapp.com/attachments/...) must be publicly accessible. Links from private servers or DMs require authentication and cannot be downloaded.
Link expiry
Discord CDN links expire. If the link was copied a long time ago, go back to the Discord message and copy a fresh link.
Supported format
ClipKeep works with direct Discord video attachment links. Post URLs from discord.com/channels/... are not currently supported — use the direct CDN attachment URL.