Apparently, Netflix always shows an error message upon hitting the play button if using private browsing (it works fine otherwise). I am not giving up on my right to use Netflix and I do not wish to give up on my privacy either, so I attempted a workaround emulating private browsing. Under Options>Privacy and Security>History I changed it to custom settings, unchecked “remember my browsing and download history” and “remember search and form history”. Cookies from sites option was set to “always” and keep until Firefox closes. Checked “clear history when Firefox closes” and checked all boxes under settings for this option. “Tracking protection” and “Send do not track” were both set to always. As far as I know, I replicated everything private browsing does but to my surprise, after restarting Firefox Netflix worked just fine. Either I missed something or Firefox sends a flag to the website, which lets it know if users are using private browsing or not. If I missed something, I would like to know what I missed so I can further improve my privacy. If Firefox sends a flag to the website about private browsing use, I would like to suggest removing it, as sites do not really need to know that kind of information. Another suggestion is to make it clear on private browsing help page (https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history) exactly what browser settings are changed upon using private browsing (instead of showing what it does as features) so it is easier to troubleshoot. If you are reading this, thank you for your time.