That he really should have had a touchdown. He had two blockers leading him, I couldn't see the numbers, but the blocker in front (Longacre #96?) ran right by Dallas' kicker and left him unblocked. Kicker then slowed down Cooper allowing others to get the tackle.
Obviously things are moving very fast at this point, but isn't the point of lead blockers to actually block?
You can see it very clearly on this video.
I think Longacre will not enjoy the video review of this play...