Wrong location. You are in exceptions. Remove that, go to the advanced menu you got there from. At the bottom, you will see “Networks”. Open that and you should see an “All Networks” antry, and below it, items for your various networks. Find the one for your extender and open it… Unselect the Use DNS entry (says whatever DNS you use for default) and select “Prefer network DNS”. Since I don’t need this, I am unsure whether you should check, or leave unchecked, Force Libre mode. Either try it both ways or maybe someone else here can tell you.