Here's a step-by-step guide to setting up an Ethernet connection on your E800:
Begin by connecting your network cable to your router.
Next, lift the cover on the back of the terminal.
Plug the network cable into the network socket on your terminal.
You can access the settings from either the login page by pressing the cogwheel at the bottom middle, or after logging into the POS, press the menu in the top left and enter settings. Both paths will lead you to the same area.
Ensure that Mobile Data is disabled under the Data usage menu. (Note: In the provided picture, it's enabled)
Navigate to the More... menu tab, select Mobile Networks and ensure Data Roaming is disabled. (Note: In the provided picture, it's enabled)
Proceed to disable Wifi as well.
Finally, restart your terminal.
By following these steps, you should be able to successfully set up an Ethernet connection on your E800.