If there's no search volume for individual product names, should I just focus on optimising category pages rather than individual products?
If your product doesn't have search volume, you can try targeting the keywords related to your product.
Let's say that your product name is "Webhosting ExampleDuck Free v2.6".
You can try targeting the keyword "Free Webhosting" and related ones such as "Webhosting for Free".
Your product may rank for the keywords that it relates to. How likely your product is to rank for these keywords has to do with your on page SEO, backlink profile and competitiveness of the keyword.
If you have inbound links coming to your product page from trusted websites in your niche, that will be a strong ranking signal for Google.