Wycombe had to settle for a goalless draw at Ipswich after missing a late penalty to extend their advantage at the top of Sky Bet League One.
Wycombe remain five points clear but second-placed Ipswich were denied an opening goal in controversial fashion two minutes before the break.
Kayden Jackson was adjudged to have turned the ball home but television replays suggested the final touch came off a Wycombe defender.
Portsmouth beat Rotherham 3-2 in a see-saw encounter at Fratton Park.
Ronan Curtis fired Portsmouth ahead inside 60 seconds with a spectacular effort, but Freddie Ladapo equalised from close range after 15 minutes.
Ben Close volleyed a superb winner from the edge of the penalty area for Portsmouth after 66 minutes.
Parkinson has won just two of his 10 games in charge with the Black Cats slipping to 11th.
Sunderland took a 19th-minute lead when Luke O'Nien was brought down by John-Joe O'Toole and Aiden McGeady converted the penalty for his sixth goal of the season.
Forest Green were held 0-0 at home by Crewe as they missed the chance to go top of League Two.
Victory would have taken Forest Green above Swindon on goal difference but third-placed Crewe proved resilient opposition.
Grimsby and Cheltenham also fought out a goalless draw as the struggling Mariners' winless run stretched to 10 games.