Hi, that depends.
This plugin is not a install and forget, you need to manually optimize scripts.
First thing you need to check, is if the frontend in incognito mode, when you view source, does it show any files pointing to the cache directory, minified? Or do they show on gtmetrix?
By default, at least the CSS files should be automatically optimized.
If they are not showing up, means there is some error (check the footer, if any html comment shows up).
Sometimes there is server or hosting cache as well, so you may not be seeing the fresh optimized page.
Can you share your url or gtmetrix report ?
Is there zero difference, or just small?
Note that sometimes, the site is just too heavy that even with optimization, it can fall short.
