Recently we've been losing the internet connectivity on our TP-WPA7617 which is in the same room as a TV using an Amazon Firestick.

After a bit of experimenting I noticed that if I unplugged the Firestick the Powerline LED came back on.

Using the app I noticed that the signal on the Powerline Adapter was down around 75Mbps.

Contacting Support we tried loads of things and eventually the solution was found. 
I had to download the Utility app onto my PC and using Advanced Settings I simply turned off Power Saving on the whole set up. I now have 150Mps and the Internet Connection works with the Firestick in use.

I hope this might help you save an hour or so!