That's good to know that a new Basic paragraph bit of text will hyphenate. I assume you created that in the same document as the non-hyphenating text?
You know I would still export to IDML and open it/save as new name, just in case. It won't harm anything if you do that in the same version.
If the problem still persists, I would try copying a non-hyphenating paragraph out of one of your frames, creating a new frame on the pasteboard, and pasting it in. Does it hyphenate?
If it does, it could possibly be that there's something glitchy with the original text frames. (I've seen this with converted Quark docs before ... rarely, but I've seen it.) Try copying all the text out of a story, deleting the frame, dragging out a new text frame, and pasting it in. If it hyphenates, there you go. You need to redo the frames in the doc.
If copying/pasting to a new text frame doesn't make it hyphenated, then I'd select the entire paragraph and make sure the Character Style was None. Still not hyphenating? Select [Basic Paragraph]. Now it should hyphenate.
When you are able to eliminate corruption of document and corruption of text frame as a cause, then remove all local formatting (in case a jokester applied No Break to every long word) and apply a bad boy paragraph style. Keep applying styles one by one till you see hyphenation gets disabled. Then look at the style definition for:
- No Language (I know you said they're set to US English but want to be thorough ;-))
- No Break
- Hyphenation on/off AND limits (maybe it says words have to be 30 characters long before they hyphenate)
- GREP styles and Nested styles that are applying a Character style that uses No Break or No Language
AM