The message on your LCD saying Please open idler and remove filament manually shows up when the extruder motor does not succeed to remove the filament from the hotend/extruder. Please do not panic, this can be solved very quickly and you do not need to abort the print.
If you get this error before a new print while you want to change the filament, first just try to load the filament again into the preheated hotend. The filament tip will melt again and it should be easier to remove it afterward. If that is unsuccessful, go through the following steps.
Troubleshooting
Follow our illustrated guide to resolve this.