@Marvin_S I already tried all of those steps. I gave up and installed a wired connection; a couple of unwanted holes in my floor, but at least it works. The PLC function of the P9 simply doesn't do...

I've got 1000 mb/s internet connection and on main router high internet speed. Because we live in a big house with thick walls, we have a TP-link Deco mesh system for wifi. Main deco is a Deco P9...