Filament Not Extruding or Under Extruding

Ultimaker 2, Ultimaker 2 Go, Ultimaker 2 Extended

There are a couple of different ways that extrusion problems can occur on your Ultimaker 2 3D printer. The nozzle could just have a blockage causing no material to come out of the nozzle at all. But you could also be experiencing under extrusion, where your Ultimaker 2 is extruding material, but inconsistently, resulting in poor quality prints with gaps, bobbles or missed layers.