See my post on the other topic - the shop needs to be marked as secure as well (ie the tiles within the shop room need to be marked as secure as well):
Looking at the image, the door on the right hand side between the terminal and the footpath is not zooned as secure, so the passengers cannot pass through the door; you’ll need to zone this as secure. Annoying, when you place a door on a section of wall, it will not be zoned secure automatically as walls tiles cannot be zoned, so the tile underneath will not be zoned when the wall tile is removed.
Once a departing passenger has passed through a security checkpoint, they can only walk on tiles …