Hi, same thread.https://community.tp-link.com/home/forum/topic/162106?page=1&t=2019%2F06%2F01%2003%3A11%3A33%20%2B0000 

Meanwhile, may I now which unit is connected to the main router by wired cable as a main unit? It is suggested to connect the 9020 to the router directly. And use the tL-WPA9610 to extend the wifi range and provide ethernet connection. 

For the wifi reception, you can change some wifi settings to improve its performance, like wifi channel and channel width. 

https://www.tp-link.com/support/faq/1611/

If it does not work, you can refer https://www.tp-link.com/support/faq/398/ to change the wifi settings of the 4220.

Besides, you can adjust its location, try to change another socket to plug it. 

May it help and have a nice day.

Yes, I now realise that the 9020 should be connected to the router. The router is in STUDY and is connected to a 9610 which is a wireless extender. 

I did this because the 9020 has 2 Ethernet ports. I have a TV and a TV receiver box in LOUNGE, both of which need Ethernet connections. Would the better solution be to swap 9020 and 9610 and use an Ethernet switch to connect both devices to the 9610?

Yes, you can connect both TV and TV receiver to 9610 by Ethernet switch. Put the wireless extender and your router in different rooms will provide you a larger Wi-Fi range.