Hi,
You need to do this:
1 - create a new product and save it, without changing anything in it.
2 - change its id in both the hikashop_product and the hikahop_product_category tables
3 - then, you can add prices, images, options, etc via the interface
If you do step 3 before step 2, then you also need to update the product_id in the other tables, like hikashop_price where the prices are stored, or hikashop_file where the files and images are stored, etc. So it will get more complex and you might miss some entries.