web browser

I suspect you have the Arcadian GW and it has updated to the newer code that doesn't have the web management access. From the community conversations I have seen on the subject I am pretty sure you will need to use the mobile application for management of the gateway. I have the prior Nokia gateway and it does support the browser management so I cannot say for sure. 
There was a firmware update to that gateway which resulted in that change. It is not a good change for the end user experience but I don't think that was the focus of that decision. Management of the appliance without the option for a physical link is a poor solution and makes it less flexible.