Website inaccessibility. [Mac.]

[danll]

OK, this is just nuts. I am running FF 110.0.1 on two machines. An M1 iMac with Monterey, and a MBP with High Sierra. Both are connected to the internet and see websites in general with no problem EXCEPT for one test website the MBP is unable to access. I get "The connection was reset. The connection to the server was reset while the page was loading." Over and over. I've tried cleaning caches on that machine, relaunching FF, and I do all hard refreshes with CMD-R. Nothing. BTW, on the MBP, Chrome is able to see that particular website with no problem. To my knowledge, I'm not intentionally blocking anything in FF on the MBP. Complicated website? Nope. It just displays "Test". That's all it does. What's going on???

[TheVisitor]

Links to the 'test site' are always helpful in verification of the problem...