You can check the Web Console (Tools -> Web Developer) for messages about blocked content and about the presence of mixed or unsafe content.

• https://developer.mozilla.org/en-US/Tools/Web_Console

You can check the Network Monitor to see if content is blocked or otherwise fails to load.

• https://developer.mozilla.org/en-US/Tools/Network_Monitor

If necessary use "Ctrl+F5" or "Ctrl+Shift+R" (Mac: Command+Shift+R) to reload the page and bypass the cache to generate a fresh log.

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• https://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History").

Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data for that domain that you do not want to lose then make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of involved files.

If you revisit a 'forgotten' website then data for that website will be saved once again.

• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

You can try to login to Facebook in a New Private Window.

You can check for issues with location storage (indexedDB).

• https://firefox-storage-test.glitch.me/

Web Console gave me this:

This page uses the non standard property “zoom”. Consider using calc() in the relevant property values, or using “transform” along with “transform-origin: 0 0”. www.facebook.com ErrorUtils caught an error:

window.performance.memory is undefined

Subsequent non-fatal errors won't be logged; see https://fburl.com/debugjs.

I think Facebook is anti-Firefox now.

I got this from Web Console:

This page uses the non standard property “zoom”. Consider using calc() in the relevant property values, or using “transform” along with “transform-origin: 0 0”. www.facebook.com ErrorUtils caught an error:

window.performance.memory is undefined

Subsequent non-fatal errors won't be logged; see https://fburl.com/debugjs.

I got something back from Web Console, but this thing won't post the error message I copied.

It said something about "non standard property "zoom"."

It said something about "non standard property "zoom"."

Hi, don't worry about zoom, that just some styling.

Did you try the above-referenced test page:

You can check for issues with location storage (indexedDB).

• https://firefox-storage-test.glitch.me/

All four test should pass in regular windows; there will be some failures in private windows.

It seems the issue got fixed by someone. Facebook works on Firefox again.