XnView Software

I noticed almost all the photos from one of my trips (all in one folder) are missing the categories assigned to them. This is in the Browser Folder view. The Categories pane with the tree selection of categories shows all my categories but none are assigned to the photos. The Category Sets pane also shows no categories under Assigned.

However, if I go to the Categories Filter tab, and click a category I know I assigned to these photos, they show up where they should, despite the category data is missing. I've tried assigning and unassigning categories but it doesn't stick. None of my other folders and files are affected this way.

If you can start from the beginning again, I think you can try to delete this entry in Tools, Settings, Catalog
Find the name of this folder in the table and delete it.

Go back to this folder and assign a category to a photo to see if it is repaired?

But if you had a large number of categories in this folder, we can look for another method to keep the work you've done.