Hi. I have had a problem with my home network since I added a TP PowerLine adaptor.
The problem I have had from the outset is that my PC connected to the HH5 wifi, but it can't ping devices that are connected via the TP Link.
My network consists of a HomeHub5, with some ethernet connections, some wifi on the homehub5 2.4GHz and some wifi connected devices to the TP link remote end.
I suspect there is some 'issue' with allowing connectivity from the HH5 wifi devices to the HH5 ethernet devices. Two of the devices on the TP Powerline adaptor wifi are happily talking to the internet and can ping the router, and the internet (google), but can't ping my pc on the HH5 wifi. Similarly, my pc can ping the router, and the internet (and surf etc), but can't ping devices on the home network connected via the TP Powerling adaptor.
Although I can't find any settings on the HH5 to restrict connectivity within the home network, it sounds too much like a security restriction to protect parts of the home network from other parts.
Have you got software firewalls running on the machines that you can't ping? These will will block most or all incoming connections unless you tell them not to.
Today, all of a sudden, two of the three Raspberry Pi's are responding and a check indicates they have switched from the TP-Link connection to direct to the HH5 wifi.