This situation usually occurs when there is no hard reference to Open Level Method Or Blueprint, for example, if you use the data table string level name, example that runtime combie LevelName FString* LevelName = Level + Index and so on, UE will not automatically cookie those map asset when packaging, at this situation , you should manually in the Project Setting under the Asset Manager, in the Map parameter, " Is Editor Only" unchecked, and then add the Map folder to Directories.
