This appears if paper is set before printing from the bypass tray starts. Follow the procedure below to remove the paper in the bypass tray.
Remove paper.
Press the [Test Paper Feed/Resume] key.
The [Test Paper Feed/Resume] key stops blinking and stays lit.
Insert a sheet of paper into the bypass tray with the print side face up.
Support the sheet with your hands to keep it from sliding out and dropping.
Insert the sheet straight into the bypass tray.
Press the [Test Paper Feed/Resume] key, and then push the sheet into the printer a little.
Printing starts.
If the rear cover is installed, follow the same procedure.