Unable to access my Three NR5103EV2

I have been using Three's Mi-Fi devices to connect to the internet for over 10 years. My second 5G device is a Three NR5103EV2. It is working OK for all my many home devices.

I am unable to access it's 'Dash board' on my Windows 11 PC and my iPhone Zyxel Air app. I have reset the 5103 using the recessed switch on it's base. I have blue LEDs for cellular signal strength and 5G internet.

I am using the Username and password printed on the 5103 base label. Three's technical support are unable to provide an answer to this problem.