Make sure you have updated the Widevine plugin to the latest version (4.10.2557.0).

• Tools -> Add-ons -> Plugins

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

Thanks for your response but nothing worked to fix the issue of netflix not working in firefox. As I said, it works in chrome and edge.

Go to about:plugins and check version of the Widevine plugin.

Thanks but I have the most recent update for Widevine. Netflix still won't play in Firefox.

Can you at least confirm what Widevine version you use as Google Chrome and Edge use their own, different, Widevine version, so if if works there then this doesn't imply that it works in Firefox ?