Thanks Stovall. Here's what Cloudflare's homepage has to say about this error:
"A 522 error means we were unable to reach the origin web server at all."
Now, not being a computer expert, I'm guessing "origin web server" relates to my web server - Mozilla Firefox.
It also says Flightsim's server might be overwhelmed at this time.
Since others have reported accessing Flightsim this morning, I have to believe it's on my end. I'll have to give things a little while to settle down.
BTW I have a couple of unrelated questions re: putting things on my computer (non-FS related) and about whether they are security risks. I'll ask in a separate question.