At 17:36 of the second period in the Ducks/Capitals game, Washington requested a Coach's Challenge to review whether Anaheim was off-side before their goal.
After reviewing all available replays and consulting with the Linesman, NHL Hockey Operations staff were inconclusive in determining whether Anaheim was off-side prior to the goal. According to Rule 78.7, "If a review is not conclusive and/or there is any doubt whatsoever as to whether the call on the ice was correct, the On-Ice Official(s) will be instructed to confirm their original call."
Therefore the original call stands - good goal Anaheim Ducks.
Since the Coach's Challenge did not result in the original call being overturned, the Washington Capitals forfeit their time-out.