How are you trying to set them up? There are several different ways to use Effekseer, although these animations specifically were designed with RPG Maker in mind. Are you trying to open them on RPG Maker MZ? Or Effekseer itself?
In order to use these on RPG Maker MZ, you need to add the respective animation folder (either Essentials or Astrology) inside your "effects" folder. You should then be able to access and load the folder and its contents easily in the editor. In case that doesn't work, please make sure that you're using the latest version of RPG Maker MZ, as some of the older versions are incompatible with newer Effekseer animations. In case you're trying to open these animations inside Effekseer itself, likewise make sure you're using a recent version of the program.
Thank you!