I'm concerned about the age of that file:

Valrotha said

bookmarks-2017-01-27_14_3eJV5Mv42kKx1Octjc6XUw==.jsonlz4

That's five months old, and most likely you've added some bookmarks in the past five months. Can you find anything more recent?

If that's the only profile folder in Old Firefox Data, you might try:

Does the Profile Manager list your immediately previous profile folder?

To check on that, inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

This page should list all the profiles Firefox is currently aware of. If you see a profile that is not currently set as default that looks promising, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but I think those are still "under construction" so please ignore them.)

Firefox should exit and then start up using the other profile. Does that one have the right bookmarks?

If so, you can create a fresh backup to a convenient location for easier restoration in your normal profile (which you can switch back to using the about:profiles page again).

If not, hmm...

Sounds that you have used the refresh feature in Firefox and have created a new profile. If you did then some personal data (bookmarks and history, form data, tabs) from the old profile would have automatically imported.

The current profile folder is moved to an "Old Firefox Data" folder on the desktop. Installed extensions and other customizations (toolbars, prefs) that you have made are lost and need to be redone.

Why do you want to restore this specific Developer Edition compressed .jsonlz4 backup? Have you ever used a Developer Edition Firefox version.

• https://www.mozilla.org/en-US/firefox/channel/

The regular release would use a xxxxxxxx.default profile folder with a possible time stamp appended in case that profile folder was already the result of using a refresh. It is possible that this Developer Edition bookmarks backup isn't compatible with the current release.

You can copy files like these to the current Firefox profile folder to recover specific data. Be cautious with copying SQLite databases if you previously had problems.

• bookmarks and history: places.sqlite
• bookmark backups: compressed .jsonlz4 backups in the bookmarkbackups folder
• cookies.sqlite for the cookies
• formhistory.sqlite for saved form data
• logins.json and key3.db (decryption key) for Passwords saved in the Password Manager
• cert8.db and possibly cert_override.txt for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words you added to the spelling checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other Site Preferences
• sessionstore.js for open tabs and pinned tabs

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 Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

@jscher2000 That did the trick! Thanks so much for your help.

@cor-el "Sounds that you have used the refresh feature in Firefox and have created a new profile." Yep, that seems to be the case. I use both regular Firefox and the dev edition which I hadn't started recently.

I fired up the dev edition which asked something along the lines of getting a fresh start, which I foolishly just assumed was an update or something. I tried copying the entire grouping of files and folders in the Old Firefox Data file (created after I did the restart) into the existing Mozilla Firefox folder located in the Program Files folder. However, that didn't fix the problem either.

Thanks for the quick responses! Much appreciated.