Press and hold the reset button to return your device to default settings. Then you may setup username and password again. Hope this help.
just go to settings, then select WLAN > WLAN Basic settings > select SSID broadcast > Disabled or if you want to put password just go to WLAN > WLAN Basic settings > WPA pre-shared key(this is where you can put your password) > then don't click box on show password. > SAVE.