In order to make them work on the fullPage.js plugin for WordPress, make sure to enable the scroll bar on the fullPage.js configuration by setting to
active the option "Scrolling > Scroll Bar".
This option determines whether to use scrollbar for the site or not. In case of using scroll bar, the autoScrolling/snap functionality will still work as expected. The user will also be free to scroll the site by dragging the scroll bar and fullPage will fit the section in the screen when scrolling ends.
You might also find these articles relevant: