Status bar (showing clock, date, WiFi, etc) wont go away in some apps

I have the new IPad Pro 12.9. In some of the apps the status bar wont go away. I have a few local video apps (HBO Nordic, DRTV) where this is an issue when watching videos. Also the same problem occurs in the Kindle app, while there are no problems with apps like Netflix and Viaplay which work just fine as they always have. Any idea if I can do something to fix this myself or if this is an issue with the app that needs an update ?