At 3:04 of the second period in the Penguins/Senators game, Ottawa requested a Coach's Challenge to review whether Pittsburgh's Trevor Daley interfered with Ottawa goaltender Craig Anderson prior to his goal.
After reviewing all available replays and consulting with NHL Hockey Operations staff, the Referee determined that Daley prevented Anderson from doing his job in his crease. According to Rule 78.7, "The standard for overturning the call in the event of a 'GOAL' call on the ice is that the Referee, after reviewing any and all available replays and consulting with the Toronto Video Room, determines that the goal should have been disallowed due to 'Interference on the Goalkeeper,' as described in Rules 69.1, 69.3 and 69.4.
Therefore the original call is overturned - no goal Pittsburgh Penguins.
Since the Coach's Challenge resulted in the original call being overturned, the Ottawa Senators retain their time-out.