You are missing the bowden clips , they are blue crescent shaped clips the slide in to prevent the white knob from sliding in and releasing the tube.
Random link I found. You can 3D print them as well.
The issue might be deeper though, if I think one step further, does your filament extrude? If the filament gets stuck, and the extruder pushes the filament it can cause this, might want to make sure your printer works too, could be an issue with the hot end.