New pictures don t display correctly in Media

Hello,

I have a problem since this morning.
When I want to upload a picture, it works but just display with a cross (see picture).
I can t reach link where is the picture, so maybe problem with link generator. (if I type http....., error 404).

I have already looked permission of wp-content and it s ok.

I m in multisite and it works for the main site but not sub.

Can you help please?

Thank you