Devolo won't connect although I have internet

[ntsannclark]

I have a wifi extender and although the signal is 'excellent' on my laptop and desk computer, the message keeps saying there is no connection. I have unplugged, waited, re plugged, re booted, re set, turned off and unplugged everything, it still says signal full and excellent, but still will not connect. One message I have received when troubleshooting is that something is unplugged. I have checked re checked and to my knowledge everything is intact. I am using an almost new Devolo dLAN 550 wifi, My laptop is fairly new, my PC is around 8 years, but runs really well. Would be grateful for some help.
Incidentally I'm sadly not a tech whizz kid...more a silver surfer, but I have a bit of savvy so please don't be too technical. Many many thanks

 

[popatim]

Since this is an extender, what is it connected to?