Can’t Upload Header Image

I’m trying to set up a website, and I’ve been having trouble customizing the header image. I successfully installed a theme that allows the header image to be customized, but each time I try to upload a header image,the image doesn’t load. I do not receive any error messages and I’m not taken to the “crop image” page. Whenever I click on the “upload” button, I am redirected back to the “Manage Themes” page. It’s starting to get on my nerves,and I’ve tried changing the header with several different themes; but none of them successfully uploaded.

Does anyone know how to fix this?