Can't connect via UART with BBT Octopus

I am continuously met with this error … klippy.log

“mcu ‘mcu’: Timeout on connect
mcu ‘mcu’: Wait for identify_response
Traceback (most recent call last):
File “/home/pi/klipper/klippy/serialhdl.py”, line 69, in _get_identify_data
params = self.send_with_response(msg, ‘identify_response’)
File “/home/pi/klipper/klippy/serialhdl.py”, line 258, in send_with_response
return src.get_response([cmd], self.default_cmd_queue)
File “/home/pi/klipper/klippy/serialhdl.py”, line 316, in get_response
cmd_queue)
File “/home/pi/klipper/klippy/serialhdl.py”, line 250, in raw_send_wait_ack
self._error(“Serial connection closed”)
File “/home/pi/klipper/klippy/serialhdl.py”, line 62, in _error
raise error(self.warn_prefix + (msg % params))
error: mcu ‘mcu’: Serial connection closed”