Let’s do a full clean re-install;

Note: Firefox comes in three or more folders on all computers. They are;

Maintenance: (Programs Folder) <Windows Only> Firefox itself: (Programs Folder) And two folders in the profile of each user on the computer for each Firefox profile for that user.

If you remove the Firefox program folder, the user profiles would not be affected.

Download Firefox For All languages And Systems {web link}

Firefox ESR; Extended Support Release {web link}

Beta, Developer, Nightly versions https://www.mozilla.org/en-US/firefox/channel/desktop/

Install Older Version Of Firefox {web link} Be sure to read everything here.

Download and save the program you want. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86) Note: Check Both Folders

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Look for, and remove any Mozilla or Firefox program folders. Do not remove the Mozilla Firefox folder if there is one.

Do Not remove any profile folders.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

How to Start all Computers in Safe Mode; {web link} Free Online Encyclopedia

Fred, thanks for the suggestion. However, I have already done that several times now and it has made no difference. I still just see the Amazon search engine. In fact, I have tried installing the latest version -- 99.0.1 -- both ways. In other words, by doing "About Firefox" and allowing Firefox to download and automatically install the update and then restart itself, and also by downloading the actual DMG file, and dropping the new version of the app into my "Applications" folder, thus overwriting the old version. Absolutely nothing has worked, and I don't know why.

As I have said a few times now, this problem started right after I upgraded from 99.0 to 99.0.1. Of that I am certain.

You could file a bug with the developers. Perhaps they can suggest some other logging or testing.

https://bugzilla.mozilla.org/

I uploaded a search.json.mozlz4 file from a recent test profile (created with Firefox 99.0) in case you want to try it:

https://www.jeffersonscher.com/sumo/search.json.mozlz4

According to my reader page at https://www.jeffersonscher.com/ffu/searchjson.html, it contains only the built-in search engines with no default set.

The problem I am now having with my bookmarks is also weird. While they all currently show in Firefox, if I export them, then create a new profile, and then try to import my bookmarks to the new profile from the exported "bookmarks.html" file, for some reason, it is NOT importing anything from the "Bookmarks Toolbar" folder. The folder remains blank after the import, while the "Bookmark Menu" folder is full after the import. So does that mean that the bookmarks in the "Bookmark Toolbar" folder are not even being properly exported? Well, I got curious, and so I opened the "bookmarks.html" file in BBEdit. And guess what? All of my links under the "Bookmarks Toolbar" are in fact listed in the file; yet for some reason, they are NOT being imported. I wouldn't mind starting from total scratch, even if it means slowly re-entering all of my hundreds of unique passwords. However, losing hundreds of my bookmarks due to failure to import them? No thanks!

If you type part of the title or URL of one of those missing bookmarks in the address bar, does Firefox suggest it on the drop-down? If so and you go to that page and click the blue star icon in the address bar, Firefox should let you view the current folder location. Possibly it is a subfolder of the Bookmarks Menu.

For future reference, you can use Backup and Restore to move bookmarks between Firefox installations (it's not cross-browser): Restore bookmarks from backup or move them to another computer.

Well, I finally got tired of all the unexplainable nonsense, so I bit the bullet and performed a clean install of Firefox 99.0.1. Before doing that, I imported my backup "bookmarks.html" file into Safari in order to determine if it would recognize all the links in my Firefox Bookmarks Toolbar. As you may recall, for some reason, Firefox was NOT importing the Bookmarks Toolbar links. Well, Safari did recognize them. So, after reinstalling Firefox 99.0.1, I imported my bookmarks from Safari, and it worked fine. The Bookmarks Toolbar links are now recognized in Firefox. Last of all, I visited all of the major websites that I normally visit, and I saved logins and passwords in Firefox. Also, once again, I can now use the search engine of my choice. Thank God that nightmare is over ... even if I don't know what caused it. You can be sure that I am going to backup the entire "Firefox" folder in the "Application Support" folder ... just in case! :)

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.