devolo adapter not connecting to plusnet router

[#1]

I have a new plusnet router hardwired to my PC (Win10) in upstairs study.  I use devolo powerline homeplugs ("1200+") to help enhance the WiFi signal in downstairs room where TV etc is located.  Base adapter is wired to router; second adapter (the WiFi one) is plugged in downstairs adjacent to TV.

Without the WiFi adapter, the TV does receive signal, just not very strongly.  In the past, the homeplugs have worked well to boost the signal.

But no longer - with adapter plugged in downstairs, the WiFi signal from my new Plusnet router is eliminated, not enhanced, and the TV doesn't make any connection at all, nor does my iPhone when it is downstairs in the same room as the TV.

So something is wrong.  I have tried resetting everything; I've made sure that the two homeplugs are properly paired, with white lights showing on both.

Today I have discovered, exploring the Plusnet Hub settings, that the router recognises the base adapter which is wired into it, but the adapter is labelled 'not connected'.  (See screenshot attached.)

I've no idea if this is the source of the problem; in my ignorance, I expected to see that it is 'connected', as the PC is.  Just in case, I have tried making the connection using a brand new ethernet cable in case the existing one was faulty, but the problem persists.

Can anyone help me to understand what is causing this problem and how to fix it?  Is something basically faulty, or is there some setting that I need to tweak?

With thanks to anyone who can help.

[#2]

Do both ends of the Powerline link have ethernet ports? If so, I would suggest trying a device wired to the plug downstairs as a first step to identify whether or not the Powerline link itself is working.

If it is, then you can move onto exploring what's wrong with the Wi-Fi.

[#3]

Thanks Bob,

Yes, the downstairs adapter has an ethernet port and I typically have a cable from that to my Sky box.  I've done some further checking....

As soon as the (paired) downstairs adapter is plugged in to the wall and establishes its steady white lights, my iPhone loses Wifi connectivity.  The TV does also.  And so does the Sky box, whether or not the ethernet cable is in place.

[#4]

Does suggest that either the Powerline link isn't working, or there's something wrong with the link between the source plug and the router.

Have you tried using a different LAN port on the router and when you say you 'reset everything', does that include the Powerline adapters?

[#5]

@RogerThornhill  have you tried using Devolo dLAN Cockpit to check connectivity ?

Here is a brief YouTube video showing what it does - Devolo dLAN Cockpit video 

Here is the Devolo download page - Devolo dLAN Cockpit downloads 

[#6]

Yes - reset power line adapters as well as router and all other devices.

And yes - tried using a different port on the router.

The fact that the router recognises the base adapter while labelling it “not connected” might confirm your suggestion that the problem lies between those two components. I don’t understand enough technically to know whether it can be fixed without buying new equipment.

[#7]

Thanks Nibiru, I will look into this tomorrow and report back.

[#8]

OK, I've downloaded the Cockpit software but (see attached) it shows no device is connected - although the base powerline adapter is hardwired into the router, as per the screenshot in my original post.  

(Must confess I don't understand the term 'PLC device', but I assume in this context it's looking for a devolo adapter.)