Your Premium Version of your Fantasy Icons does not load correctly in RPG Maker MZ, all it is showing is black. You recommending using the "IconSet.png" file to prevent that, but it is also not working.
Hey, this can be a RAM issue. But either way, if you have a image editing tool, you just need to make the Sprite sheet smaller, by removing part of the icons so your pc can load it. Just remember to only change the height(bigger number of the resolution).