Even using the latest version and UTF8-encoding on the CSV I still experienced this problem. Newly imported products show up in the back-end and I can navigate to them manually but they don’t show up on the product collection pages. Only the category totals indicated they were there somewhere. But as described by paulc8712: once you re-save the product (without making any actual changes) they magically appear!
In the wp_posts table I compared a ‘visible’ and ‘invisible’ product side-by-side, but I couldn’t find any meaningful differences. But then I checked the wp_postmeta table. I could see some rows were added to the re-saved product. Amongst them: the infamous ‘total_sales’ field. And then I remembered my standard product sorting method was ‘popularity’ (based on … total sales!).
Adding the same row for other post_id’s (screenshot) immediately fixed the problem. So if the ‘total_sales’ metatag of a product isn’t set, it doesn’t show up in the popularity grid (screenshot) but it does if you sort e.g. by date (screenshot).
So in a way this is a small glitch in WooCommerce (or the Storefront theme). But it can be easily circumvented by letting your plugin automatically add the particular custom field ‘total_sales = 0’ to new (!) products in the CSV import. I hope this helps in fixing it.
I’m not planning to click the re-save button 5000 times anyway :P!