I'd first try restoring your InDesign preferences:
There's a possible bug that's been reported before (but only occasionally) with losing export options. It has been solved by several people by uninstalling InDesign and reinstalling. Fortunately, with InDesign CC and the Creative Cloud app, that's pretty easy to do if you have to.
Renaming prefs didn't change the behavior, so I uninstalled and reinstalled.
And that worked!