Have you done the pair operation on your WPA4220? If your WPA4220's powerline light is not on, then it means your WPA4220 hasn't been paired. Anyway, you can try to press the pair button on one...

What is the model number of your TP-LINK product?

I think the buzzing sound is normal as long as we can use the products normally without any other problem. Apparently the buzzing sound is not too loud.

Guess TP-LINK has been trying to solve this problem, but it just takes some time to finish it as TP-LINK has many products to maintain.

I believe the AV500 you have seen is TL-WPA4220. You have misunderstood the PLC network speed with ethernet speed. In PLC network, 500Mbps is just like 230Mbps in ethernet. In addition, PLC network...

There is a simpler way. You can just set DMZ for your FTP server.