Is there a working example for interaction with the Things Network using AS923?

I have 2 LoPys with each acting as an OTAA node and a nano gateway node respectively.
I modified the following files as follows,

config_py:

SERVER = 'router.as.thethings.network'
LORA_FREQUENCY = 923200000
LORA_DR = "SF10BW125"

nanogateway_py:

RX_PK = {"rxpk": [{"time": "", "tmst": 0,
"chan": 2, "rfch": 0,
"freq": 923.2, "stat": 1,
"modu": "LORA", "datr": "SF10BW125",
"codr": "4/5", "rssi": 0,
"lsnr": 0, "size": 0,
"data": ""}]}

OTAA/main.py:

for channel in range(0, 72):
lora.remove_channel(channel)

for i in range(0, 16):
lora.add_channel(i, frequency=923200000, dr_min=0, dr_max=4) #not sure why cannot set DR5

The JOIN_REQUEST & JOIN_ACCEPT messages have been successfully generated. However, my OTAA node is unable to join the network.

Please advise, thank you.