Hi, your browser identified itself to the forum as version 115 on Mac OS X 10.13. Although Mozilla is still releasing security updates for the Extended Support Release of Firefox 115, many sites consider 128esr or 140esr to be their minimum version.

One option is to set Firefox to lie about your Firefox version number. This might fool some sites. Here's how:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

More info on about:config: Configuration Editor for Firefox. The moderators would like us to remind you that changes made through this back door aren't fully supported.

(2) In the search box in the page, type or paste forceVersion and pause while the list is filtered

(3) Double-click the network.http.useragent.forceVersion preference to display an editing field, and change the value to 128 or 140 then press Enter/Return or click the blue check mark button to save the change.

If you try the problem site again in a new tab, does it still give you the same message, or does something else happen now?

By the way, the reason your Firefox won't update beyond the ESR of 115 is your older version of Mac OS: Firefox users on macOS 10.12, 10.13 and 10.14 moving to Extended Support Release.

If you go to the Mac App Store -- Safari probably would be better for this -- and check for "upgrades" (rather than "updates"), it should indicate whether your Mac can move up to a newer version.

I followed the instructions; my "about Firefox" box didn't change the version number chase let me in! It acted as if I hadn't logged in before, so I assume it read the edited version number as a new browser. Neither Word nor Apple will now update my computer; I'm just trying to use it a long as possible since it works for so many other things perfectly well. I do have a new MacBook Pro, but I hate having to use multiple machines. I guess I use this fix until it quits working? Thanks for this advice.

The About Firefox dialog knows the truth, but now websites don't. We do what we gotta do, right?