have you tried pair them again by push the pair button?
if still can't pair,try to reset by push down the pair button for 15sec
or you can try to add the device manually by utility (tpPLC) ,it can be download on their website http://uk.tp-link.com/download/TL-WPA8630P-KIT.html#Utility

I tried pairing several times but was unsuccessful. As I had bought two kits I got the other main adapter and swapped it over with a new Ethernet cable. I was then able to pair successfully. Not sure why this should be as I only bought the kits six months ago and all adapters worked okay.

I may try to link in the original main adapter to see if it is a fault but after dealing with the problem yesterday will leave well alone for now!

Thanks for the advice.

Y

I have 5 units of AV1200 powerline adapters running.
The 1st week of January 2017, the furthest 2 units stop working with middle "Powerline" LED turning red / orange.
I did a reset for both but they couldn't pair with the rest of the network.
Finally I did a reset for all 5 units and they have been working since.