Lexmark MS812dn / MS812dtn
Open the rear door.
Remove the jammed paper.
Note: Make sure that all paper fragments are removed.
Close the rear door.
Push the back of the standard tray.
Insert the standard tray.
If necessary, press on the control panel.
The printer posts a paper jam error with the paper stopping at the rear door. See this article for troubleshooting steps.
Troubleshooting a 202.05 Paper Jam