After obtaining the codes you must enter one of the rooms and use the console to activate the camera that is needed for this mission. Go back to the corridor while avoiding the employee. Use any path you want to enter the room in which you started the mission. You must stay there at least until 4 PM. Then use the marked door.
You will enter another room. You must pass through it.
Use the panel in the next room. You will activate the camera (1). Now you must return to the monitoring room and use the marked door (2). Behind it there is a room you visited previously. From it you can enter the corridor that leads to the monitoring room.
After entering the room you can notice that the previously snowy screen now shows the footage from the darker room. Interact with the monitoring console to check the footage from the room in which Clay is playing cards.