Depending on your source video signal sometimes the Trueview scaler chip on the GBS can emit RF interference that effects wifi and can prevent access or changes to the web interface.
There are 2 work work around for this:
Turn off your video source and make then make any changes needed to web menue for the GBScontrol firmware.
Change the wifi channel on your wifi router to either channels 1, 6, or 11. Many wifi routers are in "auto" by default.
Channels 1,6,11 have the least amount of overlap and are less likely to have interference.