After you have selected the print job and released, the MFD will display a “resources required” warning, this is notifying you that you must enter the required media.
Select View Active Jobs
Select the print job, select Details
You will now see a screen that shows what media/paper the device requires for this particular print job. In this example, the device is asking for A4 Letterhead paper to be inserted into tray 3. If this is not what you intended to print onto or the size is incorrect, go back a screen and highlight the document and delete it. You will need to re-submit the print job ensuring that the correct size and type is selected within the application and print driver. The image below gives an example of how to do this in Microsoft Word.