Your product image is below Google's minimum resolution. As of 2026, Google requires product images to be at least 500×500 pixels for non-apparel and 250×250 pixels for apparel. Smaller images get the product disapproved.
Either the source image in your feed is genuinely below resolution, or your CDN is serving a thumbnail variant instead of the full-size original. A surprising number of feeds point at /thumbnail/ URLs without realizing it.