Have you also run your Media Library images through Optimus’s bulk optimizer? I just tried accessing the WebP version of one of your images however it doesn’t exist: https://product.hstatic.net/1000185761/product/vaporx5-next-gen-blue-rapsberry-228g_small.webp
Ah yes, my mistake. Do you have a custom setup that removes wp-content/uploads/ from your asset URLs?
Can you share how you are removing the wp-content/uploads/ section of your URL? This might be contributing to the issue here as the uploads folder needs to be properly defined in order for CE to know where to look for WebP images.
I also noticed that some of your image paths are slightly in the HTML as opposed to the asset itself in your network tab.
HTML: http://cdn.thehinh.com/2018/12/5-cach-giup-bạn-khoe-hon-1-218×150.jpg
Network Tab: http://cdn.thehinh.com/2018/12/5-cach-giup-b%E1%BA%A1n-khoe-hon-1-218×150.jpg
Is this expected behavior?
I’m not sure how to do it because it’s done by someone else, not me. But WordPress can understand my upload and self-linking, I think CE must understand where it is located.
I spoke with our developers about this and it seems that this issue is likely related to the fact that your image uploads aren’t using the default directory, therefore, Cache Enabler is unable to find and replace them with the WebP alternative. I will make a note of this and add it to features roadmap for future updates.