A few possible things going on here...

First, to turn the bookmarks toolbar on/off, you can access the toolbar list from any of these:

• right-click a blank area of the tab bar, or right-click the "+" button on the tab bar
• tap the Alt key to activate the classic menu bar, then View > Toolbars
• on the Customize tab, use the "Show/Hide Toolbar" button (Customize Firefox controls, buttons and toolbars)

If the toolbar is showing but doesn't actually contain your bookmarks, the "Bookmarks Toolbar Items" might have moved to a different bar. You can use the Customize feature (Customize Firefox controls, buttons and toolbars) to see whether you can find and move them back. If they are nowhere to be found, you can use the "Restore Defaults" button at the bottom center of the Customize tab to return to the default toolbar layout.

Any luck? If that doesn't work, I wonder whether one of your add-ons is glitching with Firefox 38?

Could you test in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

If the above didn't help and the "Bookmarks Toolbar items" is on the Bookmarks Toolbar then you can check for problems with the places.sqlite database file in the Firefox profile folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/