@Joguirian "So, the 2 kits are connected to the router" Are you saying you have existing AV500 and a new AV600 powerline adapters plugged into the router? There should only be one one active...

Looks like you are using a smartphone to measure the speed? Most phones and laptops only have 1 aerial so on best of days, you might see 50 mbps on 2.4 ghz band using TL-WPA4220. Otherwise, 36-40...

@BoltX1 Given its 10 years age, it's probably has a power supply fault if the Power LED doesn't light up. Defective/leaking capacitor common problem with all ageing electronics. When one dies, the...

I had to interrupt power to the 4220 running older firmware after 6 days. It was fine up to that point, so the test was inconclusive. I configured a static IP address on the 4220 to stop it spamming...

Another observation is TP-Link UK do not list earlier firmwares for the TL-WPA4220 v4 on their website, unlike other EU TP-Link websites.

I was using the Windows version. EXE Filename properties reports version no 2.2.3149.12. Original zip filename: PowerLineUtility_Win_180816.zip