Additional information: I tried FF on another Mac on my network and I was able to load the gui, so there's definitely something borked on my copy of FF.

I just tried a Refresh and that did not work. http is still being forced to https.

I think you're running into Mac OS Sequoia's firewall blocking Firefox from the internet. Read this article: Firefox blocked by macOS 15 Sequoia firewall - What you need to know

I think you're running into Mac OS Sequoia's firewall blocking Firefox from the internet. Read this article: Firefox blocked by macOS 15 Sequoia firewall - What you need to know

Thanks for the input, but I'm able to use FF with no issue on Sequoia. Turning off the firewall did nothing.

The problem remains that FF is forcing my router addresses to https with no way to override to http - and I cannot login to the router using https - in fact when I attempted to set one of my routers to use https it became impossible to login and I had to do a reset that cost several hours of my time.

I've searched for all manner of 'fixes' and none of them work. I did a Refresh of FF but it made no difference.

Yes, I can still login to my routers using Safari, but FF is my preferred browser and it makes no sense to me that one day it worked and the next it absolutely fails after a update.

Oh wow. I totally see what you mean now. Sorry for missing that!

I'm going to see if there's a bug filed for that because no one would expect a local network site to your router to have a SSL certificate.

This bug matches and has a workaround in comment 18: Cannot access local network sites in macOS Sequoia https://bugzilla.mozilla.org/show_bug.cgi?id=1919889#c18

I hope it helps. This is a seriously strange issue I was not expecting to see.

Oh wow. I totally see what you mean now. Sorry for missing that!

No worries, appreciate the help!

This bug matches and has a workaround in comment 18: Cannot access local network sites in macOS Sequoia https://bugzilla.mozilla.org/show_bug.cgi?id=1919889#c18 I hope it helps. This is a seriously strange issue I was not expecting to see.

I tried the workaround but unfortunately it hasn't seemed to help; I quit and restarted FF after setting the exception in Sequoia. Haven't tried rebooting the Mac yet but I doubt that will make any difference.

On the plus side FF 131.0 now seems to not be forcing https, but I'm still getting the same error message. Security tab mentions encryption - not sure if that's where the problem lies.

Considering there are millions of routers that require http://192.168.1.1 this seems like it should be fixable without compromising browser security.

See:

• https://support.mozilla.org/en-US/kb/https-only-prefs

See:

• https://support.mozilla.org/en-US/kb/https-only-prefs

Did all of that already, thanks.

As mentioned, this is no longer the issue.

I'm not sure exactly what happened, but I'm now able to access the router gui on FF!

Recent changes on my end: Upgraded to OS Sequoia 15.0.1 Double checked Mac firewall and local network settings, made sure Firefox was enabled.

FYI: I did notice today that the router gui was seriously messed up on every browser I tried, and realised that the most recent version of NordVPN has a new 'protection' feature that was enabled - after disabling it the gui was back to normal. Previously I had thought that perhaps Nord was the problem causing my FF issue, but turning it off made no difference (and having it on didn't affect other browsers).

Perhaps it was a bug in Sequoia? Whatever, I'm just glad I can access again.