@David-TP hi there. No, the units no longer connect in different rooms. We had three that had connected quite happily for months, including out to the garden room but suddenly won't. I also have a Netgear set but that won't connect either. 

We don't have any coax in the house at all. Perhaps I should have said that I'm in the UK.

The garden office us about 12m from the house. 

  @RobThrush007 

Hi Rob

Did you solve this?

We've had an Octopus Smart Meter installed and now our TPLink Powerlines don't work & we had 4 extended throughout the house and into the garden.

Quite frustrating 

JC

  @BigJC Nope. Never did. Everyone blames each other and nobody has any suggestions yet, ike yourself, it screams "of course the smartmeter is to blame, it's what changed!"

I eventually solved the problem by installing a passive powered wireless broadcaster and taking a feed from the router around the outer wall which reaches the garden office easily.