Make sure you have the latest Widevine version (4.10.2391.0).

You can toggle DRM off/on to see if that makes Firefox (re)load DRM components.

• Settings -> General: Play DRM
• https://support.mozilla.org/en-US/kb/enable-drm

You can possibly check the XHR requests in the Browser Console if this doesn't work.

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

Hi kyleingy,

Can you try the steps from the following thread and let us know if it helps? https://mzl.la/3IAHsAY

Hi,

I have updated Widevine to the newest version and Netflix player is now working. However, when I go to full screen mode the screen will intermittently flash all black for a quick instant at a time. This will happen regularly about every 15 seconds. This has never happened before and full screen mode works with other services such as youtube without the intermittent black outs. Has anyone ever had this happen before?? What should I do?

Thank you, Kyle

That's strange, for sure..

Try Firefox Troubleshoot Mode to see if the problem goes away. Firefox Troubleshoot Mode (previously known as Firefox Safe Mode) is a special diagnostic mode that temporarily turns off hardware acceleration, disables add-ons (extensions and themes) and resets some settings. See the Diagnose Firefox issues using Troubleshoot Mode article for details.

If Firefox is open, you can restart in Firefox Troubleshoot Mode from the Help menu:

• Click the menu button , click Help, select Troubleshoot Mode and click Restart in the "Restart Firefox in Troubleshoot Mode?" dialog that opens.

If Firefox is not running, you can start Firefox in Troubleshoot Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Troubleshoot Mode window appears, select "Open".

If the issue is not present in Firefox Troubleshoot Mode, your problem is probably caused by an extension, theme or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Troubleshoot Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again. (If you can't exit Firefox Troubleshoot Mode, please see Firefox is stuck in Troubleshoot Mode).

When you figure out what's causing your issues, please let us know. It might help others with the same problem.