@Oliveman Please reset RE450 by pressing the reset button with a pin for 3-5 seconds. Then refer to this to configure RE450: How to configure Range Extender via Tether APP

@mapidd You mean that connect Powerline to RE200 via Ethernet, then powerline can access to internet via RE200, just as the following? Then the answer is Yes. Router...

@Quita You have different wifi name from your router for RE450's 2.4G and 5G respectively? Your PS4 can connect to your router 2.4G and 5G both?

@BeeD The other LED will be on after configuration successfully. Please follow this to configure RE200. How to configure Range Extender via Tether APP

@Kab Please in mind that the wifi password you entered should be the same as your router's. Please provide the following information, then I can provide further help. 1. Please provide a screenshot...

@Sanners Please check below: How to hard reset TP-Link wireless access points, extenders to factory defaults