me too had this kind of problem but with "gacha nox (hallowen edition)" but, if you allow me, I can help you! you need to install something called "7 zip" then you go back to your file right click (on the gacha star file) and you will see 7 zip you leave your mouse on it, then you will see options displayed, so you press "extract here" and normally, if you try to open it it works! I hope this helped you!