I recently bought a TP-Link TL-WPA4220T KIT (an ethernet wall socket and 2 extenders). I have the ethernet unit installed correctly with an AV600 powerline extender in the kitchen and an AV600 powerline extender in the back of the house.
Sadly, the performance of the AV600's is very patchy, but it is a reasonably old house.
My main issue is that the AV600 in the back of the house has stopped working all of a sudden. It creates a wifi network, which I can join using the password, but there is no internet connectivity once joined. I have done the usual hard reset activities but it makes no difference.