We fixed a lot of things on each release so it could be possible that we now do some check properly which was not the case previously.
If a product is not displayed on the front end, first, make sure that it is published, and attached to your category. If you use the Business edition, you can also check that the access level is ok.
If the product isn't displaying on the back end either, then maybe the problem comes from the category of the product ? Are you sure that your product is linked to a valid category ? Do you see it in the table hikashop_product in the database ? If so, do you see an entry in the table hikashop_product_category for your category and the product ? If not, try to create it. The product will appear in the back end listing under that category and you should be able to edit it to see if there is a problem.