Okay, incident resolved.
I just connected my computer to my phone so as to use its LTE connection, and that worked. I am currently on vacation in a rental house. So, I don't know, nor control the WIFI configuration. (And, I don't want to monkey with it.) They must have it configured to block some connections. Internet generally works fine.
Thanks to ahoward for writing and to all for thinking about this.
Cheers,
Jamie