I don't know the V30's software, but does your launcher have an option to hide the notification bar which you might have activated by accident?
(I use a third party launcher with this option, and keep the notification bar hidden most of the time).
Otherwise, is this the case all the time, or does it just disappear when running certain apps? If the app is allowed to use an immersive mode then the bar could disappear when some apps are running.