Could be a number of issues.
Adobe Font Cache
More than one font of the same name active
Correct Unicode ranges defined in font.
Correct Unicodes applied to glyphs in font.

Thanks Malcolm. I was able to get it to show up properly. Now, the 1/8 fraction does not show up in Illustrator, but does show up in InDesign? This the same issue or something else? Thanks.

When you say it shows up in InDesign can you pick it out of the glyph pallet? If you can, does it flash-up the correct Unicode for the 1/8 fraction. Can you repeat that in the Illustrator glyph pallet? Can you generate the outline from the 1/8 glyph?

Did you do the amends in FontLab? Do you get the correct Unicode for 1/8 if you read the finished font back into FontLab?

Check the outlines for 1/8, do you have doubled-up outlines?

I would say this is a bug in Illustrator СС. I have version 17.0.2. I have tested this issue with several installed fonts and Illustrator doesn't show totally 2 glyphs: .notdef glyph (which is usually the first glyph in the font) and the last glyph of the font. Adding one glyph to the font in FLS fixes the problem for the previous glyph but the new added glyph is invisible in the Glyphs panel.

Regards,
Johnych

Thanks johnych- I emailed both FLS and Adobe and seems that Adobe AI CC has a bug. Hopefully Adobe fixes this b/c it's pretty annoying! I have been working around it by adding in a "dummy" glyph at the very end but wonder when I can stop doing this. Thanks!