Did you reset and reconfigure it? How about status of all lights in RE200 before and after you configure it? What's the firmware version?

But this kit TL-PA2010KIT contains 2x TL-PA2010 and one of them is connected to the router (as above) but the other is extender. Does it matter which item (product) is connected to the router? It...

Both TL-WPA2220 and TL-WPA4220 are OK. It can be paired to add in existing network.

All TP-LINK powerline adapters can be paired and work together. The one with similar function as PA411 should be PA4010.

Did you try different channels on Wireless 5GHz---Basic Setting page? "Enable SSID Broadcast" is checked, right? Is it brand new or it was working?

How about status of all lights on powerline adapters when disconnecting? Check local area connection on your PC. What's the IP address, default gateway, DNS obtained?