I am following these steps from the wiki:
Factory Reset / "Unbricking"
In the extreme case that a LAN Turtle has become permenantly inaccessible or inoperative, there is a quick method for recovery using a special web interface.
Download the latest factory image from https://downloads.lanturtle.com/turtle-2-factory.bin
Carefully open the LAN Turtle case by removing the two screws underneath the sticker on the bottom
While holding the button on the botto