[Discuss] Can't play Facebook videos in Firefox

[nancythewriter7 at gmail.com (Nancy Allison)]

Hi, all.

I have just switched to Fedora 28 from Ubuntu, and now Facebook videos do
not run in Firefox.

I googled this issue and found a topic about it:

https://ask.fedoraproject.org/en/question/120605/video-problems-on-firefox-on-fedora-28/

I entered the command suggested and got this result:

[theauthor at new-host ~]$ sudo dnf groupupdate multimedia
[sudo] password for theauthor:
Last metadata expiration check: 2:28:43 ago on Sun 22 Jul 2018 02:16:22 PM
EDT.
13Group 'Multimedia' is already installed.
No match for group package "gstreamer1-plugin-mpg123"
Dependencies resolved.
Nothing to do.
Complete!

I then entered the second command as suggested:

[theauthor at new-host ~]$ sudo dnf install compat-ffmpeg28
Last metadata expiration check: 2:30:13 ago on Sun 22 Jul 2018 02:16:22 PM
EDT.
No match for argument: compat-ffmpeg28
Error: Unable to find a match

I don't know what to do next to fix this problem. All suggestions
gratefully received.