I am using a single channel gateway which has quite a few limitations with LoRaWAN. It requires the end node to have an extended receive window duration for OTAA and downlink message to work. I seems cannot find an AT command to do that.
An additional problem is that since I am using a single channel gateway, I have to set the end node to use one frequency only so I use the
at+set_config=lora:ch_mask command to turn off all other channels. But I found them turn themselves back on automatically after transmission.