First, make sure the products are properly indexed to Algolia by navigating to the Browse tab of the dashboard, selecting the index containing your products, and searching for the product.
If the product does appear in the dashboard, please confirm that product has the right visibility settings. When products are only visible in the Catalog, they will not show up while searching in your store; they will only show up on the InstantSearch category page.
If the product does not appear in the dashboard, the product has not been indexed (properly). Make sure the product adheres to the requirements that Algolia's extension uses to determine if a product is indexable. If the product meets the set requirements, please reindex your products.
Should the problem persist, please turn on logging and investigate the log files for insights into any issues with your indexing process.