How to load Dynamic loading map through the Pak file

Problem description:If the map is packed with PostProcessVolume, such as the following picture:

After packing out the Pak file,Through the StreamLoad.SynchronousLoad () dynamic loading of the level, there are the following error:

If there is no PostProcessVolume in the level, it will not be reported to the wrong,and can be successfully opened. What is the problem? Is the PostProcessVolume is not set up or my code has a problem?