Smush CDN issues with GTMetrix

I am turning on Smush CDN to better optimize images and to serve scaled images. But after activating Smush CDN I received a new error on GTMetrix report “Combine images using CSS sprites” and it makes my site D score. But if I deactivate Smush CDN and activate Kinsta CDN then I do not get any errors for “Combine images using CSS sprites”.