Sounds like the Mac is setup to use the old version of Sync, and Sync needs to be updated. See this KB article - Sync your Firefox bookmarks, history, passwords and more See this KB article - [[How to update to the new Firefox Sync]]

Dec 14, 2015 9 Ways to Sync Firefox and Chrome: Bookmarks, Passwords May 09, 2019 Mozilla Firefox Mac 10.5 8 - download

How to Sync Safari Bookmarks with Chrome, Firefox and IE

Firefox Lockwise lets you securely access the passwords you’ve saved in Firefox from anywhere — even outside of the browser. Features 256-bit encryption and Face/Touch ID. Keep your Firefox bookmarks on Windows up to date with your Safari bookmarks on iPhone, iPad, and Mac with the iCloud Bookmarks extension for Firefox. iCloud stores your website bookmarks, so they are everywhere you go — on your iPhone, iPad, iPod touch, Mac, and PC. Dec 31, 2018 · To set up two-step authentication for your Firefox Sync account, open the Firefox menu and click your email address. Then, click Manage account . On the Firefox Accounts screen, click Enable next

Firefox early version history - Wikipedia

Firefox 77 Latest Download Full Offline Installer Recently Firefox has undergone drastic change from Firefox 29 final in the ui and support to Sync works on an account basis for syncing bookmarks, settings, history and tabs between machines. Like any other Web browser Firefox has also got in build download manager. Firefox: Private, Safe Browser for iOS - Free download and Jul 01, 2020 Download RoboForm Password Manager for Mac Download the latest version of RoboForm password manager for Mac today. Works with Safari, Chrome, and Firefox. Change Device Names in Firefox Sync Accounts