An occlusion has been detected. 
Insulin was not delivered. This may be due to a blocked infusion set, a damaged cartridge or a dirty or damaged piston rod. Change the infusion set. If the Error occurs again, change the cartridge as well. 
If the Error E4: OCCLUSION occurs, immediately check your blood glucose level, and then check again about two hours later, as insulin delivery has been interrupted. If your blood glucose level is high, take appropriate action according to your doctor’s or healthcare team’s instructions.