Are you running Firefox directly from the downloaded firefox.dmg file?

This is a mistake that a lot of Mac users make when installing software on their computer. If you don't move the firefox.app file from the firefox.dmg file into the Applications folder on your computer, it's not really installed on the computer.

Essentially, it's like you are running Firefox from a CD disc, which tricks Firefox into thinking that it's a new installation each time you open it. This can cause Firefox to create a new blank profile for you with the default settings and none of your data.

See How to download and install Firefox on Mac for more information.

Hope this helps.

Thanks for the suggestion Wesley. I am running Firefox from my mac's application folder on all my devices.

Do you have the remember password feature enabled on all devices that are connected to this Sync account ?

The signon.rememberSignons pref that controls this feature is part of preferences that are synced and this means that on all connected devices this setting will be the same. If you do not want to include signon.rememberSignons with syncing prefs then you set set this pref to false on the about:config page.

• services.sync.prefs.sync.signon.rememberSignons = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox