Canon LBP7780CX User Manual page 903

Close the right cover.
When paper is jammed in the paper drawer, the jammed paper is output automatically.
The message disappears, and the printer is ready to print.
If a message does not disappear
Paper or pieces of paper may remain in the area surrounding the paper drawer.
See the following, pull out the paper drawer, and then remove the paper or pieces of paper.
"Checking Paper Jams in the Paper Drawer"