1. Enter the Bootloader mode: connect the USB cable, press and hold the ‘USER’ key, then press the ‘RST’ key once. Finally, release the ‘USER’ key to initiate the code download.

2. Check if the USB cable supports data transfer by verifying if the connected cell phone supports file transfer.

3. To eliminate static interference, a common method is to hold the USB-C interface of the board with one hand while touching a well-grounded metal object, such as a metal water pipe in your home, with the other hand.

4. You can try turning your USB-C interface 180°; sometimes it works.

Connect the serial port and check whether the node is activated. If the node is not activated, refer to this link to activate it: https://docs.heltec.org/general/how_to_use_license.html.

GNSS requires open outdoor environments or try with an external antenna.

The development board is connected to the LDS antenna by default. If you need to use the IPEX interface to connect an external GNSS antenna, as shown in the figure below, move the resistor in the red box half a grid to the position of the green box.
The dashed line in the figure indicates the routing of the antenna feeder when using different interfaces.

The firmware supports it, but the default LDS antenna is an L1 antenna.