Hi,
thanks, I got it working now. After checking all different settings of my router hardware and the powerline adapters, I resetted the powerline / WiFi adapter to factory defaults an reconfigured it. Strange enough, without changing anything, it works now. I guess that it was a problem with the firmware of the powerline / WiFi adapter since the web interface wasn't available on this specific adapter as well.

I had the same issue, found it was to do with my virus checker taking control of allowable "apps" in Windows 10, got round it by disabling virus checker (McAfee), when hooking up to my pi.
you might also want to check the Windows firewall.