If parallax is not working for your fullPage.js site is because the parallax effect, as well as many other plugins which depends on the scrolling of the site, listens to the scroll event of JavaScript.

fullPage.js doesn't actually "scroll the site" as there's no actual scrollbar. fullPage.js simulates the scrolling of the page by changing the top or translate3d property of the page.

In order to get any third party parallax component working on fullPage.js you'll need to use the fullPage.js option scrollBar:true (or autoScrolling:false if you are willing to sacrify the snap effect).

For example:

new fullpage('#fullpage', {
	scrollBar: true
});

Additionally, if you want to simplify things and rely on fullPage alone, you can make use of the Parallax Extension available for fullPage.js.

It is designed to create a parallax effect for the whole background of your sections and slides.

fullPage.js Parallax Effect Extension