Solskjaer said an independent report issued as part of the match assessment by refereeing body PGMOL stated that Kean Bryan's opener for Sheffield United should have been chalked off for a foul on goalkeeper David De Gea while Anthony Martial's goal was wrongly disallowed at the other end.
"The momentum shifted for us with the Sheffield United game, but I've got the delegates' report from the ref and the two decisions were wrong," Solskjaer told a news conference on Monday.
"They've admitted their goal should have been disallowed and our goal should have stood. That's a big, big momentum changer for us. When you go 1-0 up rather than 1-0 down, go on and win that game.
"So that's fine margins and it has been the way this season, fine margins. You hit the post, it goes in or it goes out, sometimes you're lucky with decisions, sometimes you're not."
"There's not been time to do a lot on the training pitch, the boys that played are still on the recovery track from Saturday night but they have to prepare for the game," Solskjaer said.
"We want to get that mojo back, that spark. We created enough chances to score the goals now it's about feeling good, taking a deep breath and putting the ball between the posts."
Meanwhile, Solskjaer has ruled out any last minute signings on the final day of the transfer window.
"We've made decisions we feel have been good for individuals and us as well, with the young players moving on, with [James] Garner, [Tahith] Chong, [Teden] Mengi and [Facundo] Pellistri getting the chance to play more football," Solskjaer added.
"Our group is a tight knit group, we don't have too many players in excess and hopefully Jesse [Lingard] can get going and play well at West Ham as well."