device says 'no internet connection'

Wifi extender was working for a couple of months.  Now, devices show 'no internet connection'.  I am  pretty tech UNsavvy....any simple answers would be REALLY welcome. 

A device connected to adapter via ethernet cable also does not work so it seems that the adapter in the far room is not picking up anything from the adapter which is cabled into the router.  I was given a new product when I went back to shop but it feels to me like something has happened with my home internet....although it is working perfectly, wifi good, streaming movies fine etc.

Help if you can pleeeease.