I don't know why it is they wouldn't work, there's only two situations I can think of:
Situation 1: At some point I had all the blue ring particles in one giant file, turned out FH doesn't know how to export a particle file with multiple systems in it. It could be that they have had older versions installed of the objects sitting there, which causes FH to go RAGEIHATEYOU
Situation 2: Somebody's copying my particle files and renaming them for use in their own maps, and everybody with that issue has those maps