I already had this once.. did you copy an old Mediaportal.xml over an newly installed Mediaportal.xml? Reinstall did help for me, but maybe you can fix this with other methods.
Might I recommend you Uninstall Skin, and then Re-Install. Have you upgraded MediaPortal recently and possibly didnt Uninstall Skin and then Re-Install?
Look for all GUI Exif properties: MediaPortal-1/mediaportal/Core/Util/ExifExtensions.cs at 58c955866fb54a8c293afe525862bbb50c8f7b28 · MediaPortal/MediaPortal-1
And: https://forum.team-mediaportal.com/threads/4986-add-to-mypictures-plugin-ability-to-search-view-by-keyword.133895/post-1273275
Look for all GUI Exif properties: MediaPortal-1/mediaportal/Core/Util/ExifExtensions.cs at 58c955866fb54a8c293afe525862bbb50c8f7b28...
I would like one of the above IPTC metadata fields to display when viewing pictures in MP. I don't really care which, as I can...