Firebug functionality problem - No HTML element highlighting when hovering over Firebug diagnostic elements

[Luke Douglas]

For some reason, my Firebug no longer highlights HTML elements when I hover or select specific Firebug diagnostic elements.  It use to be that if I clicked on an element such as "<span class=fa fa-calendar"> </span>" in the HTML window of Firebug that it would highlight the element on the website page.  The same was true if you clicked on the Layout components.  This no longer works.  Any ideas on how to get it working again?

[Sebastian Zartner]

Could it be that you unchecked the option Shade Box Model?

Otherwise, it might be another add-on or some preference conflicting with Firebug. So, if enabling the option above does not help, you may follow the first aid guide.

Sebastian