It could be a faulty sensor on Tray 3, Try changing the Paper to a different paper size. Example: 8x11 to 11x14 or vice versa, To make sure that it displays the accept new paper size option. And see if it asks again to accept the settings. Try playing with the tray as well, it might be just misaligned. Remove / install the tray. If that doesn’t work I would say you’ll need to call for a technician for a closer look.
It should ask if the tray is opened and closed, if it does when that doesn't happen, the latch that triggers the open/closed signal must be acting up. So probably a technician is needed.
Problem just started recently where the screen pops up to confirm paper in tray 3 even when it is full. Not a big deal but have to keep confirming it all day long! Tray is full and guides are set and internal setting is set as adjustable. Not sure what else to check. Ideas?