I included a music downloaded from the elements.envato site in a video, but when I upload it to Facebook I get a Sony-related dispute.
How do I proceed? Do I open the dispute and use the license associated with the track as a document to prove that I own the rights?
The fact that the copyright claim is related to Sony is problematic, as music from Envato shouldn’t have anything to do with Sony.
Are you able to see who the claiming author is? Does it match the author from Envato?
The license is indeed the document needed to lift copyright claims. Quick note: you do not own the rights to the music though, right owners do (you may see it as semantics, but it has its importance).
You want to contact the Elements author and ask them to help you clear the claim. If the claims indeed came from them, they’d have no trouble clearing it swiftly for you. However if the claim came from someone else, they’d have to “fight” them to regain ownership, before you can lift it.