Hi, what version of RPG Maker are you on? The splash scene was added in MZ 1.8.0 so you will need to be at least on that version of RPG Maker MZ to use this plugin, but preferably you would be on 1.9.0 which is the latest version. You can update by going to Game -> Update Corescript
Viewing post in [CGMZ] Splash Screen for RPG Maker MZ comments
Hi, in the editor, can you click Game -> Update Corescript and then select 1.9.0 in "Version to Overwrite" and click ok, then save your project and let me know if it fixes the issue? As far as I am aware, there is no 1.9.1 core script, maybe you are confusing the editor version with the core script version?