USB Firmware Flasher
Use Google Chrome or Microsoft Edge on a Windows or Mac computer. Safari, Firefox, and phones (iPhone/iPad/Android) can't flash over USB.
First, make sure the gauge is awake — tap SELECT so the screen is on; a sleeping gauge won't show up. Next, make sure you're using a real USB-C data cable. If a port still doesn't show, put the gauge into flashing mode manually: hold the BOOT button (also labeled D0), tap the RESET button once, then release BOOT. Click Connect again and the port should appear. Closing other programs that use the serial port (Arduino IDE, PlatformIO monitors) can also help.
Nothing is broken — the gauge simply keeps its old firmware until a flash fully completes. Unplug, plug back in, and run the flasher again. If it keeps failing, try the manual flashing-mode step above before clicking Connect.
Only if you choose to. When the installer offers to erase the device, leave that off (keep your data) and your calibration and settings are preserved. Choosing erase wipes them, which you'd only want for a fresh start.