"3D20: The build platform has become unlevel, please re-level using the supplied leveling shim.3D40/3D45: First try releveling the build platform. If the problem persists, you may need to adjust your noozle gap which is available in the settings menu (asissted nozzle gap calibration). You can find the instructions here: self repair Please contact customer service if you have any questions, or this does not work.