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If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows a blueish highlighted shield icon at the left end of the location/address bar in case Tracking Protection is blocking content. You can click shield icon for more detail and possibly disable the protection. You can check in the Web Console what content is blocked.

• "3-bar" menu button or Tools -> Web Developer
• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• hold down the Shift key and left-click the Reload button
• press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• press "Command + Shift + R" (Mac)

Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" for websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data: "Manage Data"

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Frustrating. I'm on Windows 10 Pro, 64 bit Feature update 2004. Same problem with version 1909. The problem persists in Firefox Safe mode. Plus, I just renewed Firefox and tested, still no change. So I have now re-installed my extensions: Facebook container, NoScript, ublock Origin. I am attaching a small screen capture so we can be sure what we are talking about. Clicking or double click on the camera icon does not function.

It all works in Microsoft Edge, though.

Update: Obviously this is specific to this one computer. For example, in my shop I have another PC running Windows 10 with Firefox and it works correctly there. Since the problem is rare and probably related to the Windows configuration, I'm probably screwed. Good luck getting Microsoft to help out, right?

I have the same issue. Same specs on my computer O/S. It did not happen before this update. Only affects Firefox. Works in Chrome. I have done everything suggested. Still unresolved. Happened after latest Windows Feature update to 2004.

How do I put Chrome on my computer?