As stated, I am migrating my photo collection from digikam. I imported one or two folders to check information before proceeding to add my whole collection. On my test folders, XnView MP correctly read and imported both my ratings and my categories and added each new category correctly. Fantastic, I thought.
So I went ahead and imported my whole collection and this time it saved my ratings but no addtional categories were added.

Any ideas on why/how this happened? I didn't change any xmp settings in the meantime and I am happy that the ratings were imported but the thought of having to re-tag each image with a category is not pleasant. Is there a way to re-build or re-import my collection with a better outcome?
Mac OS High Sierra on a Macbook Pro, FYI. Your time is greatly appreciated. This program has quite a learning curve without a user manual.
Thanks!