Hi, my WP 4220 powerline adaptors are not working. All the lights are displaying as they should, power on, connected on and wifi light solid. They behave as though they are setting up correctly but there is no signal. The only signal I have is coming from the router and in two rooms I have no wifi at all even when standing right next to the adaptor. These two rooms are both upstairs but at opposite ends of the house. I am beginning to suspect it may be a wiring fault as the house is very old. 

Strange thing is that the adaptors were working fine in all rooms until we changed the wifi password. I have factory reset all the adpators, checked that the main unit is connected to the routera and also re-entered the password after I found some of the adaptors were using the old password. Our main smart TV is connected to an adaptor by ethernet and works as it should. I have ordered a usb c adaptor to test the adaptors for connection by ethernet as my macbook air does not have an ethernet port.

I hope I am missing the obvious as I don't want to spend money if I don't have too.