The default paper tray is set to the one that folds down or the paper size
in the MP tray is not letter but the print job you sent to the printer is
letter.
It is also possible that your application or printer settings are set to
manual feed in which case you press, I believe, the continue button once
you have paper in the tray. To get around this take the printer
settings off manual feed.
By the way, if the printer settings as set in the control panel are
correct, you may want to look for settings in your application that are
overriding the default, control panel settings.
