Hi,
If you're on Joomla 4, the normal search mechanism has been removed from Joomla. So both Hikashop categories search plugin and Hikashop products search plugin won't do anything, that's normal.
On Joomla 4, you only have the "smart search". For it to work, it needs to process the product data each time a product is saved.
I suppose you didn't save a product since you activated the HikaShop smart search plugin and that's why it doesn't find anything.
What you can do is to go in the smart search extension, in the backend, and click on the "index" button.
It will trigger the reindexing of all the data, including the products if the HikaShop smart search plugin is enabled.
Then, the products should show up in the search results.