DFRobot O2 sensor not responding via UART

Hi,

I'm new here, and after some help. I'm having an issue with my raspberry pi pico communicating with my DFRobot Gravity O2 sensor via UART. I can get the O2 values from the sensor in the default ‘initiative’ mode where it sends data every 1 sec and the values seem fine. However when I send FF 01 78 04 00 00 00 00 83 to sent to question/answer mode, I do not get the confirmation of mode being set (78 01 00 00 00 00 00 87) and the sensor continues to read every second giving a signal that start ‘ FF 88’ suggesting it is still in default mode (I should be getting a response starting FF 86 as per these instructions ).

Does anyone have any suggestions? Could it be a hardware issue or is it my code?

My micropython code is: 

from machine import UART, Pin
from time import sleep

uart0 = UART(0, baudrate=9600, tx=Pin(0), rx=Pin(1), timeout=500)#the UART pins are actually backward on the sensor
uart0.init(9600, bits=8, stop=1)#maybe comment out
uart0.flush()
sleep(1)

while True:

   sleep(1)
   uart0.flush()
   #request question/answer mode, expected response 'xff x78 x01 x00 x00 x00 x00 x00 x87 
   sequence_to_send =b'\xff\x01\x78\x04\x00\x00\x00\x00\83'
   uart0.write(sequence_to_send)
   if uart0.any():
       O2uart = uart0.read()
    
       print("{}".format(O2uart))
   else:
       print("O2 Sensor Error")
   #actual response "b'\xff\x88\x00\xc9\x05\x01\x01\xe4\xa8\"
   uart0.flush()
   sleep(1)
   #request read, expected response starts '\xff\x86'
   sequence_to_send =b'\xff\x01\x86\x04\x00\x00\x00\x00\79'
   uart0.write(sequence_to_send) 
   if uart0.any():
       O2uart = uart0.read()
      
       print("{}".format(O2uart))
   else:
       print("O2 Sensor Error")
   #actual response starts 'xff\x88'
 

The working code for measureing O2 from the default initiative mode is:

from machine import UART, Pin
from time import sleep

uart0 = UART(0, baudrate=9600, tx=Pin(0), rx=Pin(1), timeout=500)#the UART pins are actually backward on the sensor
uart0.init(9600, bits=8, stop=1)#maybe comment out
uart0.flush()
sleep(1)
   
while True:
   uart0.flush()

   sleep(1)
           
   if uart0.any():
       O2uart = uart0.read()
       O2high = O2uart[2]
       O2low = O2uart[3]
       O2 = (O2high * 256 + O2low)*0.1

       
       print("{}%".format(O2))
   else:
       print("O2 Sensor Error")