@Solla-topee Thanks, I have done all those things, but nothing works. So apparently it's a faulty unit (the second one). I will return it to where I bought it and get my money back.

@Solla-topee Only the wifi unit won't flash the power LED when I press the pair button. I think the unit is faulty just like the one I returned to the shop. It's a TL-WPA4220. Laterst firmware.

@Solla-topee Thank you. I will try this advice, but I can already say that the power LED does not blink when I press the pair button, even repeated times. And I don´t think it is normal to have to...

@SteveBamf @Solla-topee I have exactly the same problem. Returned the first item and got a new one in exchange, but with the same problem. The powerline LED doesn't go on and pressing the pairing...