Hi! I am just doing the London Euston - Manchester Piccadilly run on the West Coast Main Line. When the scenario starts, it tells me to Unlock the Doors. I press Y and it says Left Doors Unlocked, but no one boards. I'm sure I'm probably missing something, but I have no idea what.
You're not missing anything. The TSW passenger system is very bugged. You are ok as long as the progress marker counts down (top left of the HUD) and you can close the doors when it tells you boarding is complete and you can go.