Product explorer empty after import

After an import, the product and category explorer hierarchies are now blank.
No changes were made to configuration, I've confirmed that "Back end categories explorer' in Config / Display is "Yes".
The explorer window is there but no longer being populated. I've confirmed via SQL queries that the hierarchy is intact.
I can navigate through products via the combo boxes, but the explorer is much more convenient.

How can I fix this so the explorer is populated?
Screen shot attached.

Hi,

I think that you had an error in you csv file, and it broke the hierarchy.
Try to correct your csv file, then import again to see if something appear again in the category explorer.

www.hikashop.com/en/forum/4-how-to/72805...orer-lost.html#72805