DO YOUTUBE VIDEOS PLAY IN OTHER BROWSERS DOES CLEARING FIREFOX'S CACHE HELP [https://support.mozilla.org/en-US/kb/how-clear-firefox-cache INSTRUCTIONS HERE] DOES THE YOUTUBE PLAYER SHOW UP DOES THE PLAYER GIVE A TROUBLESHOOTING LINK DOES THE LINK HELP ARE ALL BOXES TICKED AT [https://www.youtube.com/html5 HTTPS://WWW.YOUTUBE.COM/HTML5] IS YOUR FLASH PLUGIN PRESENT AND UP TO DATE GO TO [https://www.mozilla.org/en-US/plugincheck/ HTTPS://WWW.MOZILLA.ORG/EN-US/PLUGINCHECK/] YOUTUBE AND FIREFOX USE HTML5 VIDEO NOW BUT FLASH IS FALLBACK CHECK PAGE PERMISSIONS [https://support.mozilla.org/en-US/kb/page-info-window-view-technical-details-about-page?redirectlocale=en-US&redirectslug=Page+Info+window INSTRUCTIONS HERE] ARE YOU USING CONTENT BLOCKERS (ADBLOCK, NOSCRIPT, ANTIVIRUS) ARE THEY SET TO ALLOW YOUTUBE VIDEO DID YOU MAKE SURE OR ASSUME DID YOU UPDATE TO FX45 OR INSTALL FRESH FX45 IF YOU UPDATED THEN OLD PROFILE MEDIA SETTINGS MAY BE WRONG TRY FIREFOX SAFE MODE IT TEMPORARILY RESETS SOME SETTINGS AND DISABLES EXTENSIONS BUT NOT PLUGINS [https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode#w_how-to-start-firefox-in-safe-mode INSTRUCTIONS HERE] IF ALL ELSE FAILS TRY NEW PROFILE [https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles INSTRUCTIONS HERE] IF NEW PROFILE WORKS YOUR ORIGINAL PROFILE MAY NEED A REFRESH [https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings INSTRUCTIONS HERE]