Firefox Sync doesn't copy the layout and appearance of the browser. This is because some people will customize Firefox individually based on what the computer is being used for and based on the screen size of the device. Therefore, it's undesirable to have all appearance changes mirrored. Assuming that the add-on did install properly on your device, it's just a matter of adding the button(s) for the extensions using the toolbar customization option. See [[Customize Firefox controls, buttons and toolbars]] for more information. Depending on how many buttons you already have on Firefox, it's possible that the buttons might also be in the overflow menu (displays as two right arrows in the toolbar). If that's the case, you can also move these buttons from the overflow menu into the regular toolbar by using the same customization option. Hope this helps.