Firefox does not have an autofill icon, do you have an extension that added it?

Check the add-ons manager, is there an autofill extension listed, and if so is there any error message next to it?

You can also try the method shown in the how to customize the toolbar article to see if an autofill icon is listed, and if so drag it back onto the toolbars.

Thanks. View; Toolbars; Customize; Found my icon and put it back!

Thanks