In the five-goal thriller at Old Trafford on Sunday evening, Matheus Cunha converted after Bryan Mbeumo’s original effort was blocked, although the forward appeared to handle the ball inside the box as the cross arrived.
VAR advised referee Michael Salisbury to disallow the goal, but he stuck with his original decision following an on-field review.
The decision left the Reds furious over the decision that ultimately impacted the outcome of the match.
Refereeing body PGMO is understood to have reviewed the footage and admitted an error was made in allowing the goal to count.
Forest officials were said to be frustrated both during and after the game, believing there was a clear infringement in the build-up that should have led to the goal being ruled out.
United went on to secure a victory, but the controversy surrounding the goal has dominated post-match discussion, with supporters and pundits questioning how the decision was missed despite video review being available.