jakaskerl as I said, I've followed the steps that you mentioned:
Boot into USB mode (press and hold the button while plugging in the USB)
Open device manager, select your device (won't be IP but something like 1.1)
Danger Zone --> Factory reset --> Bootloader type: Network --> Submit --> wait for success.
Unplug USB, plug in ETH.
But it didn't work, maybe it's a hardware problem…
I don't have a dip switch, but rather a button like @martin181818 showed in the first comment.