Hi Luke,
First check that the IP number you are using to get to the Brennan matches what the Brennan is displaying for its IP. (Your Router may have assigned a different IP to the Brennan).
Then, provided your Brennan can play a radio station (this checks that the Connection to your Router and the Internet is working OK) then the problem is with the device which you are using to display the Brennan's web UI.
I would suggest you clear the cache for the browser you are using, reboot the device then open the Web UI again using a new tab and the IP number the Brennan is displaying.
Fred