I’ve noticed over the past weeks that Nightly is unable to display some video and other imagery in my Twitter stream, e.g.:
Instead, I see the image area change to black with messaging like “Could not play media.” I’ve also just discovered that the two examples I’d isolated now do play, with no other change – Nightly hasn’t been updated or closed. So that makes it seem there is some intermittent character to this.
Facts: Twitter; Nightly current; new MBP with macOS 10.12.5; current Flash installed and enabled.