Scourge of War Boards

I played all missions in order, when I tried to play WL5 mission, have a message, that I need to play first mission 4 that I already played. Whats going wrong?

Did you achieve a Major Victory on WL04? You will need achieve a score of 3000 or higher to proceed to WL05.

only victory. ok thanks. I try it one more time. But that should be explained in the scenario.