Try this: https://support.mozilla.org/en-US/kb/what-to-do-if-firefox-wont-play-any-sounds

Please let us know if this solves your issue or need further help.

This shows you are running Firefox 43 the current version is 54. If not update you should for security reasons. https://support.mozilla.org/en-US/kb/update-firefox-latest-version

It also shows your running Flash 20, current version is 26 https://support.mozilla.org/en-US/kb/keep-flash-up-to-date-and-troubleshoot-problems

The reason I have outdated software was because I was using a computer at the library.When I use Chrome browser I have no problem with the sound