I have previously formatted the device with RMPrepUSB with the settings made as in the image sent by you, but nothing has changed. Now I formatted it once more and inserted an SD card with an empty Garmin folder in the root and the same image with the computer and a cable-connected device appeared on the screen.

My hope is that when a new firmware version appears, WebUpdater will replace the existing firmware in the device, not just create the GUPDATE.GCD file.