Image all white when adjusting the white RGB-curve in Lumetri Color Panel

Hi!

I´m completely new to Premiere Pro and have encountered a problem. When i try do adjust the white curve (luma) in the Lumteri Color Panel everything turns white. When i revert my changes the image comes back and the white goes away. I must be missing something since you are suppose to be able to change the curve, according to alot of tutorials. I tried Googling with no luck.

Help would be much appriciated.