Paul, you have confirmed that all four devices support passive PoE instead of standard PoE? As I know, TP-LINK has no switch which support passive PoE. In your case, you can use TL-SF1008P plus four...

Unfortunately, no such a feature...

Umm...the second light on both powerline adapters are on, right? You have no internet access? Can you connnect to WPA4220's Wi-Fi successfully? If not, can you check wired connection between PC and...

When connecting your PC to LAN port of WPA4220, can you check IP address, default gateway, DNS server obtained? If nothing, try to reset them. http://www.tp-link.com/en/faq-601.html After that, pair...

I didn't see such a function on web interface of MR3420. So if your ISP disconnects the data connection and you restart the router, the connection will be established again?

Now they just work when they are in the same room? In different rooms, since you paired them, how about status of powerline light?