THANK YOU!
I moved the PLM and ISY to an entirely different part of the house and it all works. I had tried two different outlets downstairs adjacent to my new shelves for my NAS drives and switches, etc. That was the problem. Now that I have it back, and know the problem, I will try one additional outlet that was recently installed downstairs. An electrician changed an old dryer outlet into two duplex outlets. If these work it would be more convenient. If they don't, I'll neaten up my test setup and keep it there.
Again, thank you. I am moving into a new house and all my network testing gear is an hour and a half away.