I have a number of outbuildings that I am connecting to the interent by using TP-Link powerline adapters.  I have one in my garage that is working fine with an RE550 AC1900 extender plugged into a TP-Link powerline adapter for power and from the adapter to the range extender via an ethernet cable for the internet. When I set this up, I just plugged it in and it got on with it and gave me wifi with an interent connection in the garage after about 30 seconds 

To connect to a shed (on the same mains circuit, and actually about 40 metres closer to the router than the garage),  I bought an identical RE, and powerline adapter and ethernet cable (from Amazon). Plugged it in, power happens, wifi happens, but no internet. The 2.4 and 5 GHz lights do not light up. I can see the wifi on my iPhone, but it says 'no internet connection'.

So I went and got the RE from my garage and plugged that into the powerline adapter and ethernet cable in the shed. After a few momets, it fired up and gave me wifi with interent. I took the new one and plugged that into the garage powerline adapter, and same as before - wifi but no internet. 

By swapping everything to everywhere, I confirmed it's only the new RE that doesn't work.  I tried to set it up according to the TP-Link app, got almost there and then it tells I am not connected to the internet.   So it seems that the etherent port does not do incoming.

Go to Amazon and request a return asking for a new one. That arrives and it's the same, wifi but no interent.

Could this be a duff batch?  Why does the one I've had in the garage for a month work fine, but these two recent ones don't?   Do I have to send this one back and hope for the best for a third one?