Can't play videos in Firefox

I am running Silverblue 37 and using the version of Firefox that came with the installation, not the Flatpak. Why do I not see videos on the Twitter web page and how can I fix it?

Did you do this?

" getting it to play videos works the same way as it does for the regular Fedora Workstation: find a package with the needed codecs, and install it. The one difference is that you use rpm-ostree install instead of dnf install"

What packages would I need to install?

These Installing plugins for playing movies and music :: Fedora Docs

Firefox need the ffmpeg package.

First, you need to enable rpm fusion Installing Free and Nonfree Repositories and reboot. Next, rpm-ostree install ffmpeg should provide firefox the codec, and then reboot the system again to apply the change.