[COM0]Download fail[Open port fail]!

I’m newbie to QUECTEL and while flashing I get the error in the title. Please help, here are the steps I followed:
1- Successfully building the firmware via vscode.
2- Connecting the UART to USB cable to the computer
3- Connecting the USB Power cable to a 5v power source (I did not connect the other USB to my computer).
4- I brought the switch to the open state.
5- I kept the PWRKEY button pressed for 2 seconds and waited for the green led to light up and then the blue led to flash continuously.
6- In the QCOM program, I selected the COM port of my USB to UART cable and 115200 baudrate and opened the port.
7- I sent “AT+QDOWNLOAD” build and got OK return. Meanwhile the green and blue light on the card went out. Then I closed the port in the QCOM program.
8- After entering the QFLASH Program, I chose the port of my USB to UART cable again and chose 460800 baudrate. (Necessary merge.pac file selected)
9- When I click the start button, one minute after “detect dynamic port6…” “[COM0]Download fail[Open port fail]!” I am encountering the error. Please help me !!!

After starting the module, please use Qflash tool to burn directly, and select QUECTEL USB AT PORT.

If the following serial port is not found after the module is started, you need to install the USB driver. If the burning fails after following the above operations, please change a USB cable for test