Why can't I find any products by partial match using the search bar in SpurIT SEO Image Optimizer?

Unfortunately, partial matches aren't supported due to Shopify limitations.

Starting from December 19, 2019, our app uses Shopify API 2019-10, where requests that pass a value for the title match only if the value is the same as the complete title.

Example: Your product title is "Cherokee Boys Grey Melange Track Pants".
So you should search by the complete title "Cherokee Boys Grey Melange Track Pants" to get a result, not by a partial text "Cherokee".