I tried to change the inventory gui buttons (sort, move all, etc.) using a resource pack and nothing has changed. I edited the gui_buttons.png and gui_buttons_new files located in the mod files and put them under (PACK)/assets/inventoryprofilesnext/textures/gui and nothing has changed with the buttons. Is there something I’m doing wrong?

this resource pack has support for IPN textures may be check how they did it
https://www.curseforge.com/minecraft/texture-packs/dracula-theme/files/3956729

I also made a simple example that works ipn.zip