The Cache Enabler plugin will look for WebP formatted images on the origin server. In your case, this means when parsing your pages it’s looking for images on https://www.thehinh.com. When checking for the images on your origin server I receive 404 errors:
Original format:
curl -I https://www.thehinh.com/2018/12/stomach-vacuum-la-gi.jpg
HTTP/1.1 404 Not Found
Server: nginx
Date: Tue, 04 Jun 2019 15:05:31 GMT
Content-Type: text/html
Content-Length: 162
Connection: keep-alive
WebP format:
curl -I https://www.thehinh.com/2018/12/stomach-vacuum-la-gi.webp
HTTP/1.1 404 Not Found
Server: nginx
Date: Tue, 04 Jun 2019 15:05:55 GMT
Content-Type: text/html; charset=UTF-8
Connection: keep-alive
X-Powered-By: PHP/7.2.6
Set-Cookie: bp_user-role=guest; expires=Thu, 10-Feb-2033 15:05:55 GMT; Max-Age=432000000; path=/
Set-Cookie: bp_user-registered=0; expires=Thu, 10-Feb-2033 15:05:55 GMT; Max-Age=432000000; path=/
Expires: Wed, 11 Jan 1984 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, max-age=0
Link: <https://www.thehinh.com/wp-json/>; rel="https://api.w.org/"
Where are the original images located on https://www.thehinh.com? If you’re using a CDN you’ll want to ensure that your images referenced in your pages are to your origin server (e.g. https://www.thehinh.com/2018/12/stomach-vacuum-la-gi.jpg) and then use a plugin, such as CDN Enabler, to rewrite the serving domain to your CDN (e.g. https://cdn.thehinh.com/2018/12/stomach-vacuum-la-gi.jpg).