I built a structure in a flat world and exported it into my structures behavior pack. I attempted to load the structure in my main build world but the load and export icons are greyed out even though it finds the file with a momentary flash of the buttons when I hit enter to reload the file into the structure block. I created a new world with the same settings as my main build minus the terrain and it loads just fine. I created an experimental world with with a random seed and it loaded there as well. I have had this issue with other files going into different versions of the same seed world of my main build. It appears to be completely random as other structures in my behavior pack load just fine.