Yes, I tried but since the modem is register in the WebManager App, it is not reseting the password.
Interesting. I have no experience with that particular device configured that way. However, if it is disconnected from the coax and you perform a factory reset, it would seem to me that there is no way for the SBG10 to revert back, as there is no connection to an external network. Therefore, perhaps you can go in to the SBG10 at that point via PC connected via ethernet and set it the way you want. After that, connect to the coax. I don’t know if the the password will revert at the point or not.
Disconnect the coaxial cable, this ensures any configurations pushed to the SBG10 by the ISP.
With the SBG10 powered on, press the reset button (should feel a click) on the back of the SBG10 and hold it down for more than 20 seconds. Release the reset button after the LEDs blink and turn off. You should see the default SSID indicating the unit reset. If you don’t hold down the reset button long enough, it would perform a restart (reboot) and would not revert back to default settings. Also if you don’t feel a click when pressing the reset button, it may be broken.
If these methods fail, you might have paper weight.