If Firefox says that Dashlane is incompatible but you're using the latest public release of Firefox, don't worry. You just have to upgrade Dashlane!
For Mac OS X
Update on Mac OS X by checking for updates in the Mac App Store or by opening Dashlane and selecting Dashlane → Check for updates in the top bar menu.
You just have to upgrade Dashlane and it should be working. To upgrade Dashlane, open Dashlane and select Tools → Check for Updates.
If Dashlane is not working in Firefox the first thing to check is that you can see the Dashlane icon in your Firefox toolbar. It should be in the upper right corner and marked green for "ON"
If it is gray, then check to make sure you are signed in to Dashlane.
If this icon is not there, please make sure Dashlane is "Enabled" in the Firefox Add-ons menu.
If this icon is grayed out and you are using Mac OS X, please check that Firefox is not launched in 32-bit mode.
If the icon is not here (or grayed-out) then the next place to look is in the Firefox Add-ons Manager. You can access this by going to the Firefox menu, then Add-ons. Click on the puzzle icon in the left column to see your list of Extensions. If you see Dashlane here, check to make sure it has been enabled. If not, click the button to do so (you may need to restart Firefox after this).
Note that Dashlane may also appear in the plugins section of Firefox. This is not important as it is not the add-on which is used by Firefox. Make sure you are checking the Extensions section.
If Dashlane is not here:
If the Dashlane icon is grayed out in Firefox, this may be that your browser is set to open in 32-bit mode.
The 32-bit mode is unfortunately not supported by Dashlane and Firefox must run in 64-bit mode in order to work with Dashlane.
To check that your Firefox application does not open in 32-bit mode:
You should see two impalas in the login form.
If you do not see anything in the fields, please check that your Dashlane icon is "ON" and refresh the page.
These impalas will be blue if you already have a Microsoft account, or gray if you do not have one. For more about impala colors, please refer to this guide