Blocked proxy setting on Nexus 7 install

[housemouse]

Downloaded and followed instructions...but at wifi network longpress / advanced setings never get to manual modify proxy settings, it askes for password and 'saves' it, no further. At notification bar at top left of screen, shows ''! You probably need to adjust configuration'' and ''! Waiting for traffic on port 2020''. How or what do I need to do to modify since regular installation instructions do not work? Is this a lockout/block by Nexus 7 -and/or Google Android 5.0.2 to prevent Adblock?