The InDesign files is probably corrupt. Many times, this happens with an InDesign file that has been around for a number of years that gets modified, saved, re-saved, and so on. A good example of this might be a job that gets updated quarterly, but the same file is edited and saved each time. There is a trick that works most of the time to remove the corruption, so that you can work on the file. Select File > Export > Format > InDesign Markup (IDML). Save the IDML file, then close the corrupt file that is still currently open. Next, open the IDML file you've saved, and confirm that no formatting or elements have been changed. You now have a clean InDesign file for the job.