Hi,
First, your version of HikaShop is probably not 4.0.0, since your subscription expired a while ago.
So you're using an old version of HikaShop, which wasn't made to support PHP 7.2 as PHP 7.2 wasn't released yet at the time we worked on the release of HikaShop you're using.
So it's normal you would get errors.
On top of that, your old version of HikaShop also doesn't support the recent versions of Joomla. And the products missing from the frontend is a typical issue of using an old version of HikaShop with a recent version of Joomla as they aren't fully compatible:
www.hikashop.com/forum/install-update/89...-8-9-10-upgrade.html
Updating to the latest version of HikaShop will probably fix all your issues.