When you installed Ubuntu did you tick the box labeled "Install third party software?" When we tick that box we get some very useful audio & video codecs that are free to download and use but are nonetheless proprietary software. Non-free in the sense of not being open source.
Without those audio & video codecs certain types of audio & video files will not play. Those codecs come in a package called Ubuntu Restricted Extras. If those codecs were not installed as part of the installation of Ubuntu then this command will install them.
Code:
sudo apt install ubuntu-restricted-extras
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