Problem linking to media

I usually install my own WordPress on servers, but I am working with a private host (client’s choice) who preferred to do it themselves. I’ve uploaded images to the media library, and can see them there. However, when I try to link to them, either for a header, background, or in a page, I get a broken link, and the images do not show up on the site. The URLs are correct, so I can’t understand why. Does anyone have any thoughts on what might be wrong? Communication with the private host is slow….