On a couple of sites that I frequent, and also occasional video links from twitter and such, I am unable to play the links or the embedded videos because i end up receiving an error. No video with supported format and MIME type found. This error only shows up if I am using the private browsing feature on my firefox quantum 59.0.2. If I go to the same site in another window that is not using the private browsing feature, it plays the video with no problems. I was wondering if there is a solution? Many times the videos play the first time around (while private browsing) with no issues. I then return hours later to view the same video and i start to get that error. I have tried refreshing firefox, and some of the other tips given here but they still don't solve the issue. Any assistance will be greatly appreciated.