Problem was intermittent and worsening under Win 8.1 Pro. Got Win 10 installed, along with the Win 10 version of Bitdefender, and then zero internet access. It will not call up a website, but only the ASUS RT-AC66R router. I can transfer files to and from drives on an NAS in my network. Not other PCs. Used Google Chrome and MS Edge, different wiring and connections, the wireless capability of the router, and nothing. Re-installed Win 10. Nothing. I think I've looked at every possible thing that might be changed in the NUC or the OS.
I sure hope someone has an idea!
Thanks!