I've been on Notebook for a long but each time I try to add a custom cover to a notebook I create, it takes a big amount of ti to process it, and then when it is already uploaded, I select it, however sometimes the cover doesn't even change, and other times, when I restart the app or I check it in another device, It turns out it did never change the cover! I don't know how to solve it, I've tried repeated times but I just cant have custom covers