What does the E1 error code mean and how do I fix it?

The E1 error appears when the [START/STOP] button was pressed while the arm cuff is not applied, the air plug is not completely plugged in, the arm cuff is not applied correctly, or air is leaking from the cuff. To fix it, turn the monitor off, insert the air plug securely, apply the arm cuff correctly, or replace the arm cuff if it's leaking. (Page 35)