I cannot upload a photo to an existing Wordpress website. I get an http error. The photo or something eventually displays in the media library - but shows as a gray rectangle. If I try to edit it - the photo displays, but it tells me the image data is not available. It will not insert into a page.
Wordpress version is 4.9 and all plugins are updated.
How big is the photo? What is the photo's source (camera, download, etc.)?Sometimes when you are uploading a large photo (1MB), you can run into resource problems if you are on a small managed wp or cPanel plan. There are several good threads throughout the community on memory/resource allocation in WP.
Keep in mind image loading is a huge reason web pages slow down. You might consider a plugin like WP Smush to optimize your images. Its by far the best image optimizer I've discovered.
Hope this helps,