The route introduction has a missing instruction. At a point it tells you to set the throttle, but does not tell you to close the doors. If you did not close the doors, the throttle is locked and you cannot unlock it any more. It is an annoying issue, because you do not need to open the doors and since this introduction is intended for absolute beginners, this is a serious bug into my opinion.
Yes, I purchased Hauptstrecke Hamburg - Lübeck in the Steam winter sale and encountered this issue too. Fortunately, I am experienced enough to work it out but OP has a point - the introduction is intended for absolute beginners and the instruction to close the doors must be included.
Usually the game would just close the doors for you as seen on Riesa-Dresden. They usually don’t tell you to close the doors. But yes, I just picked up this route and ran into that exact same issue.
