Summary: What solves the problem?
The E3 error indicates a blade motor fault, usually caused by an obstruction or overly tall grass. Follow these steps to remove the blockage and restore normal operation.
Router or network provider has been changed.
Machine stored over winter or not used for a long period.
Machine cannot reconnect automatically to the previous WiFi network.
Reconnect the machine to the previous WiFi network.
Download the Unlock file from the official Landroid account and apply it.