My theory (no evidence or grounds just speculation) is that it was intended that Harry travel on the same plane as William, Edward and Andrew to Balmoral. I find it plausible that William ignored his texts about travel - but I think it was arranged by 'the firm' that Harry travel on this flight.
Harry wanted Meghan on the flight as well - he was told Meghan cannot come. He threw his toys out of the pram and an argument/negotiation ensured around this. This delayed the flight (which was filmed sat on tarmac waiting for over an hour waiting for departure). In the end they get fed up of waiting for Harry and leave.
Harry is apoplectic at this and organises his own later flight.
William et al arrive too late - the Queen has died whilst they were enroute. They are livid because if Harry hadn't delayed them they may have made it in time.
This is the reason that Harry gets the cold shoulder in Balmoral, everyone is furious with him. Charles, William and Camilla leave to avoid a confrontation when he arrives and stay out of sight until he leaves the next day.
They announce the Queen's death whilst Harry is enroute as by this point, everyone is so furious with him they no longer care what he thinks