The root problem is that (without Packman and without any HW-provided decoder) gstreamer cannot play h264, while ffmpeg can (using libopenh264-8), so players based on Gstreamer don’t play while player based on ffmpeg play at least the h264 level provided by libopenh264-8.
Try e.g.
gst-launch-1.0 -v playbin3 uri=file:///path/to/some/video.mp4
or
ffplay /path/to/some/video.mp4