Hi Brian, it's solved!! I did two things which may (or may not) have been the last things to fix which made it start working again but I'm not 100%. First, I ran the Windows Update diagnostic a few times but I've done that previously which didn't seem to do anything (it keeps detecting and 'solving' issues but the issues keep getting detected so I assume it wasn't really fixing them). The other thing I tried was something you made me thing of about your last question: I unchecked the 'Use automatic configuration script' option in Internet/Connections/LAN settings. As I said, I'm not sure one or both of those things got it over the hurdle or not but I wanted to pass along in case helpful for others you're working with that have similar issues. What I am certain of is that it wouldn't have gotten resolve without all your help and so THANK YOU VERY MUCH FOR ALL THE TIME AND EFFORT YOU SPENT HELPING ME.
Donation gratefully made - you guys rock, keep it up!