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Ubuntu - Video - Install h.264 decoder

H.264 (High Profile) decoder is required to play the file, but is not installed.

sudo apt install gstreamer1.0-plugins-bad

NOTE: Once this package is installed, open the video file again and see if it works now.

There is the option to click on the Find in Ubuntu Software button, but suggested not to.

Clicking on that option opens the Software Center and it may (or may not) show some packages that will install the h264 decoder on your system.
But it is not easy knowing which package to select in this case.