PROBLEM:

I have six TP-Link TLPA8010P Adaptors in my Powerline network and three of them mysteriously stopped working overnight.

I tried rejoining the powerline network using the one second button press on a working adaptor and then a one second button press on the broken adaptor and this did not work. The lights flashed for two minutes and then went out.  I then tried resetting the adaptors completely using the six second button press and then tried rejoining the network again. Still not working.

SOLUTION:

The solution was to use the tpPLC Utility available at https://www.tp-link.com/uk/support/download/tl-pa8010p-kit/#Utility. On the back of each Powerline adaptor is printed a Powerline Key. I made a note of all the keys of the non-working adaptors. I then plugged them into a wall sockets ready for joining to the network. Once the tpPLC application was running and the computer was connected to a working adaptor, in the application I clicked on "Add a Device". For each non working device I entered the Powerline key printed on the back of the device and click the OK button. The Powerline adaptors then joined to the powerline network and started working again. Success!

I hope this post is useful to anyone with the same problem.