Can't insert images into posts

I can’t insert images into a post. The add media box opens, I can select the image, but when I click insert into post, it goes back to the post with no image.

I have also tried copying and pasting images into my post but I get a no image box in the published post.

I have recently deactivated all plugins and activated again for another issue that was resolved by that, but this issue is still a problem after that.