The error message "Paper Size Mismatch" or "Size Mismatch" is displayed when the paper size setting does not match the size of paper in the tray.

Or, you did not set the paper guides in the tray to the indicators for the paper size you are using.

To clear the message, follow the steps as below.

1. Check that the paper size you selected on the machine's display matches the size of the paper in the tray.
2. Make sure you loaded the paper in the Portrait position, by setting the paper guides at the indicators for your paper size.
3. After you have checked the paper size and the paper position, press Black(Mono) Start or Color(Colour) Start.

If printing from your computer, make sure the paper size you selected in the printer driver or your application matches the size of paper in the tray.