Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response - raspberry-pi3

Question

I' trying to connect from raspberry 3 B to a Modbus device (sensor temperature) using a serial connection using a USB RS485 converter .This is my code:
from pymodbus.constants import Endian
from pymodbus.payload import BinaryPayloadDecoder
from pymodbus.client.sync import ModbusSerialClient as ModbusClient
from pymodbus.constants import Defaults
Defaults.RetryOnEmpty = True
import time
import logging
FORMAT = ('%(asctime)-15s %(threadName)-15s '
'%(levelname)-8s %(module)-15s:%(lineno)-8s %(message)s')
logging.basicConfig(format=FORMAT)
log = logging.getLogger()
log.setLevel(logging.DEBUG)
def run_sync_client():
while True:
#try:
client = ModbusClient(method='rtu', port='/dev/ttyUSB0', timeout=9, baudrate=9600, parity='N', stopbits=1, bytesize=8,reset_socket=False) # Implementation of the SHT31 as a modbus serial client
if client.connect():
print("connected")
print ("begin reading")
#for i in range(0 ,100):
request = client.read_holding_registers(address=0 , count=2, unit=4)
if request.isError():
print(request)
else:
print("Read OK! " + str(request.registers[1]))
time.sleep(1)
print(request)
result = request.registers
print(result)
temp= BinaryPayloadDecoder.fromRegisters(result, Endian.little, wordorder=Endian.little )
temperature= temp.decode_16bit_int()
print( temperature)
time.sleep(4)
# except:
#print("An exception occurred")
client.close()
while True:
if __name__ == "__main__":
run_sync_client()
The output in the console is:
connected
begin reading
2022-02-24 14:56:37,901 MainThread DEBUG transaction :139 Current transaction state - IDLE
2022-02-24 14:56:37,902 MainThread DEBUG transaction :144 Running transaction 1
2022-02-24 14:56:37,904 MainThread DEBUG transaction :273 SEND: 0x4 0x3 0x0 0x1 0x0 0x2 0x95 0x9e
2022-02-24 14:56:37,905 MainThread DEBUG sync :76 New Transaction state 'SENDING'
2022-02-24 14:56:37,906 MainThread DEBUG transaction :287 Changing transaction state from 'SENDING' to 'WAITING FOR REPLY'
2022-02-24 14:56:38,068 MainThread DEBUG transaction :375 Changing transaction state from 'WAITING FOR REPLY' to 'PROCESSING REPLY'
2022-02-24 14:56:38,069 MainThread DEBUG transaction :297 RECV: 0x4 0x3 0x2 0x17 0x58 0x2c 0x2e 0x3f 0x88
2022-02-24 14:56:38,071 MainThread DEBUG rtu_framer :237 Frame check failed, ignoring!!
2022-02-24 14:56:38,072 MainThread DEBUG rtu_framer :119 Resetting frame - Current Frame in buffer - 0x4 0x3 0x2 0x17 0x58 0x2c 0x2e 0x3f 0x88
2022-02-24 14:56:38,073 MainThread DEBUG transaction :465 Getting transaction 4
2022-02-24 14:56:38,074 MainThread DEBUG transaction :224 Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response
I would love to have a little help understanding the error I'm getting. Thanks