Hi Dan, the "Home" toolbar button should be among the optional buttons you can add from the Customize panel. This article will get you there: Customize Firefox controls, buttons and toolbars.

Can you find it and drag-and-drop it to the desired spot? If the house is nowhere to be found, you could try the "Restore Defaults" button at the bottom of the Customize panel and see whether it shows up back in the box.

Note that in Firefox 87+ the Library and the Home button aren't present by default on the Navigation Toolbar and you need to drag them out of the Customize palette to the toolbar.