Yahoo has changed its add-on:

On August 1, 2016 we will simplify the Firefox Yahoo Toolbar and upgrade your browser to the New Tab by Yahoo extension experience. This extension provides a static version of Yahoo Toolbar and customizes your new tab page with Flickr photos and quick access to your top sites. Please note, you will no longer be able to modify your toolbar layout.

Source: https://downloads.yahoo.com/faqfirefoxtoolbar

That's all I know about what's going on.

Old versions of the Yahoo toolbar are available on this page:

https://addons.mozilla.org/firefox/addon/yahoo-toolbar-and-new-tab/versions/

Users have reported success installing the May 18th version; I haven't heard any reports yet on the newer July 26th version.

You can turn off updating for the toolbar on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Find Yahoo toolbar on the right side and click the tiny More link under the title, then on that page, find the row for Automatic Updates and set it to Off.

Please post back with your experiences, other Yahoo users are asking the same question.

Regarding bookmarks, if you meant Yahoo bookmarks, I only know what I posted before.

If you meant Firefox bookmarks, could you tell me where you have looked?

• Bookmarks Menu - button the toolbar, or classic menu bar

• Bookmarks Toolbar - is the bar displayed at all?

If the toolbar isn't displayed, you can use one of these methods to show the toolbar list and turn it back on:

• right-click a blank spot on the tab bar (or the "+" button)
• tap the Alt key to activate the classic menu bar > View > Toolbars
• in Customize mode > Show/Hide Toolbars (see: Customize Firefox controls, buttons and toolbars)

To turn on the Bookmarks Toolbar, Menu Bar, or other bars, click it on the list.

If the bar is displayed but does NOT have your bookmarks, let me know and I will describe the next steps.

It appears Yahoo Bookmarks may be exported from Yahoo and imported in to Firefox. Firefox is good at handling bookmarks.

Please see

• Why did Firefox screw up my Yahoo Toolbar?

John99 said

Did you also follow the link from James to Yahoo's explanation about their bookmarks (https://downloads.yahoo.com/faqfirefoxtoolbar } :

Where can I see my bookmarks on Yahoo?
Sign in to My Yahoo. Click on the "Add Content" button and add the "Bookmarks" module to your page to see your links.
How do I export my bookmarks to another browser?
You can export your bookmarks here. { USA link - https://us.data.toolbar.yahoo.com/v1/bm/tools?.intl=us)
How do I uninstall Firefox Yahoo Toolbar?
1. On the Firefox browser, click Tools | select Add-ons.
2. Click Remove, next to listing of Yahoo Toolbar.
3. Restart Firefox.

I presume using the export bookmarks link will allow you to import the links in to Firefox itself See also

• Our own help article Import Bookmarks from an HTML file

Please see the help articles, some include animations and short video clips

• Bookmarks in Firefox
• Use bookmark folders to organize your bookmarks
• Address bar autocomplete suggestions in Firefox_changing-results-on-the-fly
• Bookmark Tags - Categorize bookmarks to make them easy to find