Actor Landscape has empty bounds

I am completely new to UE (currently I am trying the EA of UE5).
Whenever I creat a new level, I can do whatever I want, it disappears as soon as I re-open the project. I always get the same error message “Actor Landscape has empty bounds”. What does that mean? (:D) Does anyone know a solution for that problem?

If you’re using world partition in UE5, the cells are probably just not loaded when you reopened the level. Try opening Window > World Partition, selecting the cells around your location, right clicking and loading those cells.