Duet not connect in anyways - Clue: nozzle fan always on
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@genioluiz7 if the Erase jumper was definitely not in place when you ran Bossa, then sadly I think the flash memory of the main processor on the Duet as been damaged. The only other possibility I can think of is that the 3.3V rail is low, perhaps because something powered by it is drawing excessive current. If you have a multimeter, you could measure the voltage between the 3.3V and ground pins of one of the endstop connectors.