Hi, if you haven't already, try restarting Firefox. If that doesn't help, go to the 3-bar menu > Customize, and look in the palette, from where you can drag them to a toolbar. If the buttons are still missing, try clicking on Restore Defaults. More Customize Firefox controls, buttons and toolbars.

It is also possible that one of your add-ons or any theme is causing this, so try disabling them one by one - or several at a time, to see if that reveals anything. Note that you might need to restart Firefox to fully disable some of them.

If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!

You can check for problems with the extensions registry files in the profile folder.

Try to to reset the extensions registry and rename extensions.json (extensionsOLD.json) and rename/remove previously used extensions files like extensions.ini and extensions.sqlite when present and rename/remove compatibility.ini in the Firefox profile folder with Firefox closed.

• https://support.mozilla.org/en-US/kb/Profiles

New files will be created when required.

See "corrupt extension files":

• https://support.mozilla.org/en-US/kb/unable-install-add-ons-extensions-or-themes

You can check for possible updates in case of issues.

• click the cogwheel button (left of the Search bar) on the about:addons page to "Check for updates"

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data