The fix I posted 2 years ago here is for a very specific case: You open a JPEG file in GIMP, and the JPEG file has EXIF tags that say the photo was taken rotated. (This happens if I shoot in portrait mode - camera rotated 90 degrees - using a camera with a built-in orientation sensor.) GIMP displays a dialog: "According to the EXIF data, this image is rotated. Would you like GIMP to rotate it into the standard orientation?"
You can pick Rotate or Keep Orientation. There is also a check-box "Don't ask me again". If you check this box, then pick Keep or Rotate, GIMP will do what you say when importing this image, and all future JPEG images, without asking. There is no way in the user interface to undo "don't ask me again", it seems.
GIMP calls this setting a "parasite" (possibly because it is attached to a plug-in, the JPEG importer) and stores it in a file called "parasiterc" in your GIMP preferences directory, which is ~/.gimp-2.8 on my system. It's somewhere else on Windows and Mac, probably.
To clear the setting and have GIMP ask you again about importing JPEG files which have EXIF rotation tags, you can either delete that "parasiterc" file (possibly losing other preferences too, but not your main GIMP settings), or edit it to remove the exif-orientation-rotate action. If you chose to do either of these, do it while GIMP is not running. Or, you can copy the command I gave above - parenthesis and all - into the script-fu console and press Enter to execute it. You do not have to restart. It takes effect the next time you open or import a JPEG file.
Both of those work, but only for the specific case I have described. If you are having a different issue, they won't help.