So at my friend's house, whenever it rains or bad cloudy day, there is no WiFi signal sending from main floor to 2nd floor. So I recommend them to install a Linksys RE6400 range extender to boost the signal, on the existing Linksys AC1200 unit, and the setup of that extender is wacky. It somehow works after a while, but w/o the 5GHz band. But the other day when they re-plug in that extender, there is no signal (even on a sunny day) So today, I try to help them to re-initialize that RE6400 by going thru the instruction, totally no signal(on a sunny day). Now, assuming it's a defective DOA unit, is there some range extender that is high quality ? And has a nice and simple setup software? (just in case pushing the WPS button doesn't work) And more importantly, should we unplug the extender when you don't use it? Or are you suppose to always leave it plug in? If you unplug it, would you lost all the setting on that extender?