Firefox 59.0.2/3 on MacOS 10.12.06 will not play streaming videos from view.yahoo.com - I tried several different videos. Symptom: When I try to play a video I get a black box, clicking on it has no effect. Sometimes I get a brief image from the video in the black box along with a small black box off to the side, but both quickly disappear. What I can do: I can play videos from youtube and pbs. Some other browsers, eg. chrome, will play the yahoo videos, but initially Safari would not, giving the same results as Firefox. When I choose the Safari per website option to disable content blockers, the previously brief image remained and I could then play the video. What I tried: I disabled all the content blockers I could find, including: ad blockers and flash restrictions. I reinstalled Firefox, going from 59.0.2 to 59.0.3 with no change in behavior; I reinstalled flash. I tried restarting Firefox in safe mode, with the same results as above. I prefer to stick with Firefox, so are any suggestions to fix this problem? Thanks, John