I have posted extension discovery results. I have not installed any extensions except Artio and JoomHack, so there are no other extensions that can have been unsuccessfully installed. I can only copy and paste what the software reports. You are correct, I did not uninstall Artio, because the suggestion was to disable it.
I understand it may not be replicated elsewhere. I have the same problems sometimes in my job when a customer tells me his machine is doing something and I cannot make it happen. It is usually down to customer error, and I hold my hands up to not really understanding all the whys and wherefores of Joomla, hopefully trying to make something simple and readable.
But i do appreciate your input.