First, I don't have Netflix so anything I write is second hand...

Silverlight

Next to your post (Question Details > More System Details) your plugin list doesn't show that Silverlight is installed. This could be if it is actually not installed, or if it is set to "Never Activate" on the Add-ons page. You can check that first, either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Plugins. On the right side, scroll to the bottom and look for "Silverlight" and if possible, change its general permission to "Ask to Activate" (the default).

If it's not there or says it's too out of down, try (re)installing Silverlight from this page: https://www.microsoft.com/getsilverlight/get-started/install/default.aspx

HTML5 + DRM add-on

The major streaming sites are planning to switch to using the built-in HTML5 video player. A useful diagnostic page for that player is YouTube's. Usually the first five boxes are blue, the last red. Could you check:

https://www.youtube.com/html5

Silverlight does not load or run automatically instead an install screen appears, processes then says Extraction Failed (The Operation Completed Successfully). You have to go, to your downloads folder and open it there, since it was saved to your hard drive. Silverlight 5 (5.1.50901.0) version was confirmed as installed.

HTML5 Video Player reads as follows; All Blue 1. HTMLVideoElement, 2. H.264, 3. WebM VP8, 4. Media Source Extension, 5. MSE & H.264, 6. MSE & WebM VP9 (The HTML5 Player is currently used when possible)

Netflix was running fine in my current Firefox browser until recently without Silverlight. After the Silverlight install and restarting my browser Netflix works great as expected.

Thanks A lot!