Hi Leilani I had this problem too (summary blocks not displaying the product photo I wanted) and reached out to customer support. Here's the answer:
The images displayed at the Product Page, Summary Blocks and Product Blocks are the product thumbnail images (added to the "Options" tab of the product), check out this guide to edit this image: https://support.squarespace.com/hc/en-us/articles/205845358-Changing-a-product-s-thumbnail-imageWhen you add a new product, a product thumbnail image is added to the "Options" tab automatically, sourced from the images added to the product at the "Item" tab, however, if you edit the product images, the thumbnail will not update automatically.