[opensuse] how to play MP4 files on Firefox

I am running Firefox 60.4 under 42.3. In the past I was able to play .mp4 files using my browser. A recent trial failed. What am I doing wrong and how can I view these files? don -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org