Connecting WiFi disc to power line adapter via Ethernet

[Hoopless]

I want to extend my network into a shed at the bottom of the garden. I was under the impression that I could connect from a WiFi disc via Ethernet into a power line adapter to reach the shed. 
The issue I’m having is that when I plug in the adapter to the disc, it gives me a solid red light and will no longer connect to the internet. 
Using TP-link AV600 power line kit

any suggestions welcome.s

[licquorice]

Why not simply use a WiFi hotspot power line adapter?

Are the 2 mains sockets used on the same consumer unit?

[Hoopless]

Both plugs of the power line kit are connected to the same consumer unit, yes. The wiring in my house is terrible so I was hoping to avoid most of it by plugging the power line adapter into the socket in the kitchen where the spur was taken to go into the shed which is all new cable.
My WiFi disc is is also plugged in here so assumed I could use the Ethernet port on that to connect it to the internet and then be able to access it via the WiFi adapter plugged in the shed.

I had considered a WiFi hotspot and running cat6 to it but the power line was the cheaper and supposedly easier option. 

As soon as I connect the Ethernet to the adapter in the kitchen the disc goes red and no longer shows as connected in my BT app