Hi @urshobhit ,
WP Offload Media Support Team here. Thanks for reaching out with your query, we would be happy to assist!
Could you check for us the thumbnail sizes of the images that don’t get offloaded? Then, please find the size in the “Names and Dimensions of Image Sizes” section of your Diagnostic Info. Your diagnostics can be found in the Support tab of WP Offload Media.
If the size is not listed there, you will have to register the thumbnail size using the add_image_size function of WordPress.
https://developer.www.ads-software.com/reference/functions/add_image_size/
Once the size is registered, you can then try running Regenerate Thumbnails. The plugin should trigger the offload of the thumbnail sizes.
https://www.ads-software.com/plugins/regenerate-thumbnails/
Let us know how it goes for you.