The loopback test is expected to fail on the Nano Every. The reason is that, unlike the classic Arduino boards like Uno, Nano, Mega, the connection to the computer is done via a dedicated serial port on the microcontroller and the port connected to pins 0 and 1 is a separate one (Serial1). The loopback test relies on pins 0 and 1 being connected directly to the USB adapter chip on the board.