Hi,
Okay, it looks like you have very few product category links ; the table is not empty but we can make better tests.
Can you please click on the tab "SQL" and paste that query
SELECT p.* FROM `hjquf_hikashop_product` AS p
LEFT JOIN `hjquf_hikashop_product_category` AS pc
ON p.product_id = pc.product_id
WHERE p.product_type = 'main' AND pc.category_id IS NULL;
If the query return you some elements, these element will be the "lost" products.
So you will be able to use that query
INSERT INTO `hjquf_hikashop_product_category` (category_id, product_id, ordering)
SELECT 2, p.product_id, 1 FROM `hjquf_hikashop_product` AS p
LEFT JOIN `hjquf_hikashop_product_category` AS pc
ON p.product_id = pc.product_id
WHERE p.product_type = 'main' AND pc.category_id IS NULL;
and it will put every "lost" products into the category "product category" (which have by default the id "2").
It's not a real button but the effect will be quite the same
Regards,