When you say that it isn't displaying the section, do you mean that the entire HTML file doesn't show up, that a paragraph is missing, that the contents of the span is missing, or something else entirely?
BTW, you shouldn't use the
font tag. It isn't a supported tag in EPUB, and ADE has this tendency to explode in flames when it sees things it doesn't recognize.
Use
<span style="color: gray;">...</span> instead.