Hello there,

I suggest trying the "Refresh Firefox" feature which usually fixes most problems. https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings

The "Refresh" feature works by creating a new profile folder for you while saving your most important data.

If the above won't work then you can go ahead and reinstall Firefox.

Give those steps a try and see if the issue still persists!

Hope this helps!

The "3-bar" Firefox menu button should always be at the right end of the Navigation Toolbar, whether the menu bar is visible or hidden.

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

• Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

• https://support.mozilla.org/kb/get-started-firefox-overview-main-features
• https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox
• https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox

rdkill said

... I have the Menu bar unchecked so the button should be there. The menu bar works fine when I have the option checked, it is just the Firefox button is missing when I don't have the menu bar enabled.

Showing a Firefox button when the Menu Bar is not check-marked was a feature in the Firefox Four thru Firefox 28 versions. With Firefox 29 and later versions there is no Firefox button - there's nothing displayed when the Menu Bar is hidden.