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?

Firmware verison of your WA750RE is up to date? Universal mode should be the right one. Besides, according to your description, the RE is running as well. That WA750RE is using smart IP or static IP...