Modern browsers block mixed content. If your primary site uses HTTPS but your dubbindosite link points to an HTTP mirror, the link will fail. Ensure both bound sites have valid SSL certificates.
Unlike a standard URL, which simply points to a single resource, a dubbindosite link maintains a dynamic relationship between two endpoints. When one version of the content is updated (e.g., subtitles are added, a video track is changed, or a file is compressed), the link automatically updates the secondary site to reflect those changes. dubbindosite link
Most advanced content management systems (CMS) use a hash-based binding system. You need to create a unique identifier that tells both servers, "These two files are linked." Modern browsers block mixed content