Hi nathanpalmer, to research this, please do not delete your current (not working) profile. But for comparison:

New Profile Test

This takes about 3 minutes, plus the time for some testing.

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

Click the "Create a New Profile" button, then click Next. Assign a name like Mar2020, ignore the option to relocate the profile folder, and click the Finish button.

After creating the profile, scroll down to it and click the 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 so we can get a clean test.

Do the videos play in the new profile?

(If needed: Allow or block media autoplay in Firefox)

Comparing Profiles

Assuming videos play in the new profile, you can compare its window with one in your regular profile that is not working. Here's what I would compare:

Load the same news page and look at:

(1) Enhanced Tracking Protection

At the left end of the address bar, click the shield icon and see whether anything is blocked on either page. Any difference? Any improvement if you unblock?

(2) Site Permissions

At the left end of the address bar, click the lock icon and see whether the drop-down shows any customized site permissions or blocks. Any difference between the two profiles?

(3) Add-on buttons

In your regular profile, extensions such as Adblock Plus, Blur, Disconnect, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix should provide toolbar buttons 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 may need to click the button to see what's going on and test whether you need to make an exception for this site.

Any improvement?

(4) Cache

In case there is a mix of current and old files in your cache, see: How to clear the Firefox cache

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

(5) Fox News cookies

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?

If we haven't discovered the culprit yet, it might be related to a less obvious setting that will take further research.

Thank you for the reply jscher2000 .

Not working profile is already deleted. I may be missing something in that reply:

Is any of this supposed to get working settings or profile into my existing Firefox Account Sync settings? It doesn't sound like it will. Am I wrong?

I have a working profile right now that has all the critical customizations working. So I'm not really interested in corrupting my current profile by syncing my settings to perform the tests you are describing if it won't get the working settings or profile I'm using now into my account sync.

I can always build my customizations from scratch in every Firefox install. The Sync would be handy to save me all that extra time though.

Is the process you described Step 1 and a Step 2 would still be required?

If I understand the current status, you have a working profile but you don't have any of the data you normally get from Sync.

Something brought in by Sync is causing the problem, whether it is a setting or an add-on or maybe some cookies. The steps I suggested would help you if you want to try to troubleshoot what the problem is with the data brought in by Sync. There is no guarantee we'll figure it out.

But if you don't want to do that right now, this thread will stay open.

You can try to rename prefs.js to prefsOLD.js to see if that makes a difference in case there is a problem with user set preferences stored in the file.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

At some point perhaps you'll want to erase the data in your Sync account and start fresh with new data. I'm not sure of the safest way to do that, but perhaps another support volunteer has a suggestion, or it might be covered in one of the support articles.

jscher2000 said

If I understand the current status, you have a working profile but you don't have any of the data you normally get from Sync.

Correct!

jscher2000 said

Something brought in by Sync is causing the problem, whether it is a setting or an add-on or maybe some cookies. The steps I suggested would help you if you want to try to troubleshoot what the problem is with the data brought in by Sync. There is no guarantee we'll figure it out.

Correct! I disabled all add-ons, etc. after Sync no change occurred to reverse the break in video playback.

jscher2000 said

At some point perhaps you'll want to erase the data in your Sync account and start fresh with new data.

This was one of the approaches I was interested in as well. I just didn't figure out how to do that.

It seemed like the first time I sync'd my data all the data went upward to the cloud. Since then it seems all the data downloads to the local device.

I don't know how to upload new data and destructively replace the current data in the cloud. I tried a few things, but my efforts failed in that regard. Every time I attempted to sync, the error was downloaded to my local device.

So I have a working Firefox install now, but I don't know how to sign into my Firefox account and get my current install up into the cloud and ignore all the previous data that is in the cloud right now.

I wish there were a Sync Upload option separate from a Sync Download option.

Once upload or download direction is determined, Maybe it would be helpful to have an option that would list and let users compare current device settings and cloud settings, then let the user check boxes on which version to keep - local or cloud - and blend the best of both settings going in either direction.