Error E4 means the air fryer was plugged into a 220-240V outlet.
Fix: Turn off and unplug the air fryer immediately. Plug it only into a standard US 120V, 60Hz household outlet.
If That Didn't Work: The error may persist. Unplug the unit for 10 minutes to allow it to reset fully. Then plug it into a confirmed 120V outlet and try again.
Heads Up: Using the wrong voltage can damage the appliance and void the warranty. If the error remains after connecting to the correct outlet, contact Customer Support. Do not continue use.