Have you installed all included DLC's for Train Simulator Classic? These are required for passengers to enter or leave the train. Don't ask me why haha.
As for the checkmark: After playing the U1 Addon for more than 335 hours with exactly 45 standard scenarios on the U1, I can tell you that there are two scenarios on which I got the checkmark. ("[05] 00:12 Uhr ab GH" and "U1 Fuhlsbüttel Nord nach Farmsen")