No way to add Header Image

Hello, I will try to explain my problem. My Wordpress is fully updated. It's in french to when I talk about a button or an option, it's perhaps not with the exact label. I indicate them with simple quotes. Sorry. With High Response theme and some others like Photfocus, I want to set an Header Image. So I navifgate to Appearance => Customize => Header Media => Header Imag, Then I enable on 'Homepage/Frontage' Then I click on 'Add a new image' button So I'm fowarded to the Media to choose an image I choose an image (enough large to be an header image) then click on 'Select and resize' button Then, I'm forwarded to a new white page 'Resize image' with 2 tabs 'Umpload files' and 'Media' But I do not see the selected image, the page is blank And when I click on the 'Select end rezise' button, nothing changes! So, No way to add an Header Image. This problem is the same when I try with another themes like Photofocus. Have you ever seen this issue? Could you help me? Thank you in advance Regards CPC