By default, Nimva 3 will have the Smooth Scrolling effect enabled.This will create a smooth scrolling experience and also the scrollbar will be thinner and less intrusive to user experience.
Changing the Smooth Scrolling effect is done by navigating to Theme Options -> General Settings -> Smooth Scrolling
If by any reasons you cannot scroll down the page, set this option to Off. Also check the custom jQuery code or any plugin you may have activated recently. It may happen to break the Smooth Scrolling effect, thus breaking the the scrolling up and down the page completely.
Written by RockyThemes