I added a "Places Maintenance" app that is supposed to repair a damaged places.sqlite file, but it didn't work.

How do you mean; it didn't work? Did you get an error or something? Or was it the history was now restored?

Forgot to ask, are your bookmarks intact?

Problems with bookmarks and history not working properly can be caused by a corrupted places.sqlite database file.

Open a new tab or window. type about:support in the address box and press enter. Or Press the Alt or F10 key to bring up the tool bar. Then Help > Troubleshooting Information.

Under the page logo on the left side you will see Application Basics. Under this find Profile Folder. To it’s right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Locate the file. Then rename or delete it. Restart Firefox.

Sometimes the only way to recover from a corrupted places.sqlite file is to delete (remove) this file to force Firefox to create a new file. Firefox will try to rebuild the bookmarks from the most recent JSON backup in the bookmarkbackups folder.

See also:

• 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