Add New Page/Folder Is Blank On Chrome/Firefox

Hello, I just install Grav, because I interesting with a website that use this CMS, very unique. With all confusing, finally I success install Grav very well. But one, event I want to add Page/Folder of page, I get blank page on my Chrome and Firefox, when I try use Opera, thats look good.

Any something wrong with my installation? Thank you....