RAK4600 - Arduino Uploading failed

When trying to upload Arduino code into the RAK4600 Evaluation Board, I am met with this error as shown below:

Repository Used:

From the repos linked above, I understand that I have to download the appropriate packages/libraries for Arduino, flash the feather bootloader and then short RX1 and GND together and then press the reset button to get the EVB into DFU mode so that I can upload the Arduino codes. However, I am still unable to get the Arduino codes uploaded.

Some steps that I have undertaken are:
Deploying a virtual test environment on both windows and linux, but back to the same error.

Is there any other way for me to upload the codes? Thanks!

Some Notes:

Flashing of bootloader command:
pyocd flash -t nrf52 feather_nrf52832_bootloader.hex

Tools Used:
CH341 Serial Driver

Hardware Used:
Jumper Wire (To short RX1 and GND)
Multi-meter (To test connectivity between RX1 and GND)

(I do not own a J-Link tool)

Just to verify.
pyocd flash -t nrf52 feather_nrf52832_bootloader.hex
output was OK?

Any other application active that might use the COM port? Arduino Serial Monitor and Serial Plotter are closed? I had a bad experience with my 3D printer app Ultimaker Cura to block all Serial ports while running.

The output seems fine.

As suggested, looking over at the device manager, I disconnected possible devices that could have been using the serial port. Serial plotter and Serial monitor was closed as well nor was I using the RAK serial port tool.

However, it is still unable to upload.

Yes, the output of the the bootloader flashing looks ok.
I just repeated the steps on my RAK4600 EVB and when connecting RX1 to GND I can flash the module without any problems.

In ArduinoIDE when you open Tools->Port, is there only one COM port listed or several ports?

Looking at both the ArduinoIDE and device manager, it shows 1 serial port being used which is the RAK4600 EVB.

Here is a picture of the board connection just in case. (Brass stand was used just for easier picture taking)

Is there possibly a different way to boot into DFU mode?

There is unfortunately no other way to put the device into DFU mode.

The only thing I can recommend is to flash the original firmware again. Check if the EVB gives any output.
Then retry to flash the Arduino Bootloader.

By output do you mean as such?

What if there’s no output?

If there is no output at all on the Serial port, you should first try to flash the original RAK AT-Command firmware with DAPLink as shown in the documentation.

After successful flashing the AT-command firmware check again with the Serial tool for any output.

Once it is clear that the RAK4600EVB is working try again to flash the Arduino bootloader.