I have a customer perspective chosen in OmniFocus settings “badges” menu for “Show in Today”. I see nothing in the Today OSX widget for OmniFocus. The OmniFocus header shows but no content.
Is it possible that the widget is the OmniFocus 2 widget rather than 3?
If everything looks fine, you should write in with a bug report to ofpreview@omnigroup.com where they can track it or help you find a solution.