I thought it was because Mane sliding tackled the goalie and missed the ball?
i think they are calling a foul against Mane, although I think it is his leg dragging and tripping Ogbonna, either way there was no foul by Mane on either player. It was a ridiculous decision from Friend.
But after last season I feel zero sympathy for Liverpool, they are now just experience what every other team (outside of United) have dealt with since VAR came in.