If you have tested your website on PageSpeed Insights or GTmetrix and you got the message “Preload Largest Contentful Paint image”, it means that the image in question is not preloaded.
Unfortunately, none of the ShortPixel plugins can help preload the LCP element. However, if you’re using ShortPixel Adaptive Images, as shown in the example above, you can try going to Settings > ShortPixel AI > Exclusions and adding the image to the “Don’t lazy load” box. This won’t necessarily remove the warning in PageSpeed Insights, but it will almost certainly improve the LCP time.