Structure blocks do not work when exporting a recent structure. If you save a structure by importing it into a local world, you cannot load it into another local world or server, neither downloaded from the internet nor recently created structures.
When selecting a mcstructure file to import a structure, the game usually does not load the structure. Even if you import a structure from a local world to another world, it usually does not load the structure. This includes msctructures that you download from the Internet.
Please do not duplicate your previous report MCPE-203319
That report is waiting for you to provide more information. Please read the comment there carefully and provide all of the requested details.