At 18:53 of the third period in the Canadiens/Blues game, St. Louis requested a Coach's Challenge to review whether Brendan Gallagher interfered with Blues goaltender Carter Hutton prior to Charles Hudon's goal.

After reviewing all available replays and consulting with NHL Hockey Operations staff, the Referee confirmed no goaltender interference infractions occurred.
Therefore the original call stands - good goal Montreal Canadiens.
Since the Coach's Challenge did not result in the original call being overturned, the St. Louis Blues forfeit their time-out.