It seems to be due to licensing problems with non-open codecs and the particular browser (audio controls show correctly in chrome, but not in edge). You should re-encode the video using supported codecs to get audio controls to show.
However, volume can be controlled on all browsers via javascript (this works even on firefox).
The long solution should be to disable default video controls and implement a custom UI to control video and audio.
For a temporary fix, the video will be muted automatically on loading.
It seems to be due to licensing problems with non-open codecs and the particular browser (audio controls show correctly in chrome, but not in edge). You should re-encode the video using supported codecs to get audio controls to show.
However, volume can be controlled on all browsers via javascript (this works even on firefox). The long solution should be to disable default video controls and implement a custom UI to control video and audio.
For a temporary fix, the video will be muted automatically on loading.