When I first tried to set up and register this Kindle, it was “Unable to Connect” during the registration process, although it appeared to be connected to WiFi.
Turns out in 2016 an update was required to allow continued use of WiFi (background info here: Old Kindles will be disconnected from the internet unless you update by Tuesday - The Verge)
SOLUTION: Follow the directions found here to manually install updates which reenable WiFi: https://www.amazon.com/gp/help/customer/display.html/ref=hp_200529680_touchupdate?nodeId=200790650 (This model is Generation 4.)
Works like a charm! Hope this saves some people from returning perfectly good Kindles.
Cheers!