Issue: When loading images into media library, only a blank thumbnail shows. After testing compatibility of plugins, themes, php, etc, problem persisted.

Go to Dashboard -> Settings -> Media
Make sure the default file path is there. When I was troubleshooting this issue on monadnocknaturalhealth.com, the file path had been /home/drgenecler/domains/drgeneclerkin.com/private_html/wp-content/uploads. When I removed this, the image file upload worked again.