RAK811 Firmware Upgrade Error

Hi guys, I recently acquired a RAK811 v1.2 and currently testing it. I followed the guide (https://downloads.rakwireless.com/en/LoRa/RAK811/Application_Notes/) on how to get started with RAK811.

I flash the bootloader then the firmware (RUI_RAK811_V3.0.0.11.H_Release). However, after upgrading successfully, my RAK811 does not respond to my commands. Even if I reset it, it would not show any data. I am also cautious with boot, 3.3V, and CND pins. Can someone guide me through this?

Update: I tried flashing the firmware v2.0.3.4 and it suprisingly it works. RAK811 would respond to my commands. However, when I flash the firmware v3.0.0.11 back, the RAK 811 would not respond to any of my AT commands again? Any suggestions? Thank you

Hi,@ton12
the bootloader has two versions have been updated,the firmware (RUI_RAK811_V3.0.0.11.H_Release) needs the newest bootloader : https://downloads.rakwireless.com/en/LoRa/RAK811/Firmware/RUI_RAK811_BOOT_Version3_0_1.rar.
You need update bootloader first.