Final update: Turns out my web host as a data cap on my plan (100gb), it also has a file count cap on my data plan (40K files). Although I was only using 5% of my data, I maxed out the allowed number of files. Support tech did an audit and I had 40,004 files uploaded. I had multiple versions of my website on the server going back to the early 2000. Most of them work from a version using a template that made many versions of photo files for thumbnails and other insertions in the theme. Downloaded and archived the most relevant files and deleted everything else.
Problem solved. Now I can upload without problems and plugins install without problem.
Moral: When dealing with tech support, ask the same question(s) several time different ways and in different orders. It took 3 calls to tech support, each time starting do describe my problem slightly differently to finally get to the right answer. Any mention of wordpress, theme templates, plugins, etc led us down a cul-de-sac, with the tech saying the problem was outside their area of support. Even when I offered relevant hosting/server related information during those calls, they couldn’t see past the idea that WordPress was somehow involved in my issue. Only on the last call when I only mentioned server related information based on what I was experiencing with my ftp client did we resolve the issue efficiently.
