Ah, Ted, I was just reading THIS POST - and realised that was what happened just over a week ago; I installed a (brand new shiny ubiquity) network router, so all IP adresses were new.
after restart of Homey, it had found the Plugwise devices again.
I do understand this should not be this way - it should have found them itself? does it help you if I send you diagnostic report? Or is it too late because it’s resolved?