there are several tracks The first step is to clear the cache https://support.mozilla.org/en-US/kb/how-clear-firefox-cache After the other step is to do a reset http://mzl.la/15sSfJR

best regard, #fxhelp #Firefox64SUMOWeek

Hi GoodLuck1, unfortunately the image upload failed. If the first reply doesn't solve it, could you attach the image to your next reply? https://support.mozilla.org/questions/1243762#question-reply

Same problem here :

https://www.reddit.com/r/firefox/comments/a60fss/youtubes_sidebar_menu_is_missing_in_ff64_on/

And also in Chrome :

https://www.reddit.com/r/youtube/comments/a35eeu/sidebar_missing_blank/

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• hold down the Shift key and left-click the Reload button
• press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• press "Command + Shift + R" (Mac)

Clear the Cache and remove the Cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" from websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Manage Data

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Thanks for replies. Not sure where hang up was. I did the usual cache n cookies clesr in addition to reinstall, ect. A day later after nothing of note it blinked on as I closed youtube/firefox & has worked since. :/