Justin,
Are you working with the lactual font as live Type, or an outlined version?
In any case, you should know that Illy is particularly particular about the quality of fonts, because she can work with them at a deeper/higher level than most, so you can easily have a font that works in all other applications, but Illy refuses to recognize it as a font.
Some failing fonts discussed in earlier threads have turned out to have rather basic flaws, such as redundant, superfluous, or (if I remember rightly) even stray points, or other clear errors in the paths that they consist of.
So if the font is flawed, you may need to look for similar fonts that Illy is willing to work with.
There may also be something funny about GPU preview, so if you have that on, you may try toggling between GPU and CPU with Ctrl/Cmd+E, or you may try disabling the GPU Performance by clicking the Rocket Icon in the App bar, or on the top of the menu bar, and deselecting the GPU Performance check box; you may also uncheck GPU Performance in your Preferences.