Various Web Developer tools each have their own pref on the about:config page to enable or disable them, so you can check if they are all enabled.

You can search for devtools.*.enabled via the Search bar at the top of the about:config page.

• devtools.debugger.enabled
• devtools.errorconsole.enabled
• devtools.fontinspector.enabled
• devtools.inspector.enabled
• devtools.layoutview.enabled
• devtools.netmonitor.enabled
• devtools.profiler.enabled
• devtools.responsiveUI.enabled
• devtools.scratchpad.enabled
• devtools.styleeditor.enabled
• devtools.tilt.enabled (3D View)
• devtools.toolbar.enabled
• devtools.webconsole.enabled

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

• Do NOT click the Reset button on the Safe Mode start window or otherwise make changes.

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

You can check for problems with preferences and rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default values.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

Yeah, done all that and still have the same problem. Shift + f2 doesn't work either. It's as though it doesn't exist, even though everything is set to true on about:config

Did you try Safe Mode?

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

Download a fresh Firefox copy and save the file to the desktop.

• http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-mozilla-central/

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Yes, I tried safe mode. I have also previously tried with a new profile, and with fresh installs. Is it possible some other software I have installed is affecting it?

Do other bars at the bottom show like the Add-ons bar and the find bar?

Yeah, those work.

Any errors in the Error Console (Ctrl+Shift+J) about this or doesn't open that window as well?

Yeah, that window doesn't work either.

Try to ask advice in the MozillaZine Builds forum.
Maybe someone there knows what is wrong.
I still have all developer tools on Linux in the current Nightly build.
I assume that you use the 32 bit build because 64 bit builds for Windows aren't tested and can be broken at any time.

You need to register on the MozillaZine forum site in order to post at that forum.
See http://forums.mozillazine.org/viewforum.php?f=23

Alright, will do. Thanks for the help anyway.

You're welcome. I hope that you will be able to fix this quickly.

With which daily build did it stop working?