@Gerry941 Hello, 

Sorry for the late response, may I know are you able to pair WPA8630 with the main adapter right now?

>It is recommended to put 2 Powerline units in the wall sockets and use the pair button to pair it

> Later plug the 3rd powerline unit in the same room, and pair 3rd one with the 2nd adapter by pair button 

Here is a guide to add extra powerline unit into existing powerline network by pair button referring to the instruction:
https://www.tp-link.com/support/faq/1081/

Note:  press Pair button only for 1 sec, if the Power Led does not blink, press it again.
When the Powerline Led or House Leds are on, the pairing process is done.

If the above does not work,please refer to this instruction to pair the powerline units/ add an extra powerline unit by Powerline Key: 
https://www.tp-link.com/en/support/faq/1615/