Make sure that [Auto Paper Select] is selected.
Place the originals, and then press [Start].
Only the paper trays specified to [Do not Display] or [Recycled Paper] in [Paper Type] and also specified to [Yes] in [Apply Auto Paper Select] under [Tray Paper Settings] can be selected in Auto Paper Select mode. Trays with a lock mark () will not be automatically selected. For details, see "Tray Paper Settings", Connecting the Machine/ System Settings.