Hi khablow, one of the differences you might see in a regular vs. private windows is which extensions are running. In order to run in private windows, extensions usually need to be individually enabled.

So my suggestion is, in a normal window double check the content blockers:

Extensions such as Adblock Plus, Blur, Disconnect, DuckDuckGo Privacy Essentials, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix usually provide a toolbar button to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you sometimes need to click the button to see what's going on and test whether you need to make an exception for this site.

You also could test in Firefox's Safe Mode. In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" Help > Restart with Add-ons Disabled
• (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart. A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Oh, and also, private windows do not share cache and cookies with regular windows. So another suggestion for your regular window would be:

Cache and Cookies: When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

See: How to clear the Firefox cache

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, click the lock icon at the left end of the address bar. After a moment, a "Clear Cookies and Site Data" button should appear at the bottom. Go ahead and click that.

In the dialog that opens, you will see one or more matches to the current address so you can remove the site's cookies individually without affecting other sites.

Then try reloading the page. Does that help?

I tried all your suggestions. I had AdBlocker Plus running and I removed it before restarting, I cleared the cache. Nothing worked. Maybe I should uninstall Firefox and re-install it.

By uninstall do you mean clearing all your Firefox data and starting clean? You can pre-test that this way:

New Profile Test

This takes about 3 minutes, plus the time to test your problem site(s).

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Take a quick glance at the page and make a mental note of which Profile has this notation: This is the profile in use and it cannot be deleted. That is your current default profile.

Click the "Create a New Profile" button, then click Next. Assign a name like Nov2020, ignore the option to relocate the profile folder, and click the Finish button.

Firefox will switch your default profile to the new one, so click the Set as Default Profile button for your regular one to avoid an unwanted surprise at your next startup.

Scroll down to Nov2020 and click its Launch profile in new browser button.

Firefox should open a new window that looks like a brand new, uncustomized installation. (Your existing Firefox window(s) should not be affected.) Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system to get a clean test.

Do the problem site(s) work any better in the new profile?

When you are done with the experiment, you can close the extra window without affecting your regular Firefox profile. (Nov2020 will remain available for future testing.)

The new profile worked. Of course, when I go back to my default I still have the same problem. How do I correct the default profile?

Well, the Safe Mode test ruled out your extensions, so it must be a setting. But... which one?

If you use DNS over HTTPS in your regular profile, you could try turning it off to see whether that makes any difference. This article will get you to that setting on the Options page: Firefox DNS over HTTPS.

In that same dialog you can find the settings for proxy server. The default of "Use system proxy settings" piggybacks on your Windows/IE "LAN" setting. "Auto-detect" can lead to a flaky connection. You may want to try "No proxy".

These changes might not take effect right away due to the DNS cache. You may need to exit/restart Firefox to test whether they make any difference.

Actually the safe mode test worked. My question now is how do I get my default profile to act the same. Under Privacy and Security I have "Don’t enable HTTPS-Only Mode" checked. I do not see proxy settings.

Okay, if you can see the content in your regular profile in Firefox's Safe Mode, the most likely culprit is one of your extensions. Something privacy related perhaps? I think I mentioned the most common suspects before.

I don't know. It was working fine, then without doing anything it started to block content on some sites. What if I use the test profile as default and start over? Will I lose all my password settings? If so I will just live with it.

You can copy over some files from your regular profile to your new one for logins and bookmarks/history. That might reduce the pain.

I'm going to list this out in excruciating detail to avoid misstating something.

(A) Open a File Explorer window for each profile folder

In Firefox, type or paste about:profiles in the address bar and press Enter to load the page.

This page should list at least two profiles, each of which has two folders and one or more buttons. Do not use any Remove buttons!

Regular Profile

Click the "Open Folder" button on the row that says Root Directory for your regular profile. File Explorer should pop up.

This is the "Source" folder and I suggest docking it to the left side of the screen by holding down the Windows key and tapping the left arrow. Or you can just make it a regular resizable window on the left side of the screen.

Test Profile

Click the "Open Folder" button on the row that says Root Directory for the Nov2020 profile. File Explorer should pop up.

This is the "Destination" folder and I suggest docking it to the right side of the screen by holding down the Windows key and tapping the right arrow. Or you can just make it a regular resizable window on the right side of the screen.

(B) Transfer key data files

Close/Exit your Firefox window(s) and give it several seconds to shut down. We don't want any files to be locked.

Right side Destination window

Right-click > Rename each of the following files:

• logins.json => loginsOLD.json
• key4.db => key4OLD.db
• places.sqlite => placesOLD.sqlite
• favicons.sqlite => faviconsOLD.sqlite

You may wonder why you are renaming these files when they are brand new anyway. It's in case you've mixed up the two windows or need to roll back.

Left side Source window

Select the following four files by single-clicking the first one and Ctrl+clicking the other ones:

• logins.json
• key4.db
• places.sqlite
• favicons.sqlite

Then right-click any of those files and click Copy.

Right side Destination window

Right-click a blank area and click Paste.

[In theory, you can repeat with other files. This article has tips on what you might want to look for: Recover important data from an old profile]

(C) Start Firefox and check for the transferred data

If Firefox starts in your regular profile, you can use the about:profiles page to check your Nov2020 profile.

Success?

That's excruciating OK. I'll go over this when I have time. I'll try to sort it all out. I have several Firefox support pages bookmarked. These are very detailed and very good.

Thanks for all your help.